diff --git a/lib/selectors/chat-selectors.js b/lib/selectors/chat-selectors.js
--- a/lib/selectors/chat-selectors.js
+++ b/lib/selectors/chat-selectors.js
@@ -569,7 +569,7 @@
 const baseMessageListData = (
   threadID: ?string,
   additionalMessages: $ReadOnlyArray<MessageInfo>,
-) =>
+): ((state: BaseAppState<>) => ?(ChatMessageItem[])) =>
   createSelector(
     (state: BaseAppState<>) => state.messageStore,
     messageInfoSelector,
@@ -618,7 +618,11 @@
   const messageInfos = useSelector(messageInfoSelector);
 
   const containingThread = useSelector(state => {
-    if (!threadInfo || threadInfo.type !== threadTypes.SIDEBAR) {
+    if (
+      !threadInfo ||
+      threadInfo.type !== threadTypes.SIDEBAR ||
+      !threadInfo.containingThreadID
+    ) {
       return null;
     }
     return state.messageStore.threads[threadInfo.containingThreadID];
diff --git a/lib/selectors/socket-selectors.js b/lib/selectors/socket-selectors.js
--- a/lib/selectors/socket-selectors.js
+++ b/lib/selectors/socket-selectors.js
@@ -37,13 +37,14 @@
 // We pass all selectors specified in stateSyncSpecs and get the resulting
 // BoundStateSyncSpecs in the specs array. We do it so we don't have to
 // modify the selector when we add a new spec.
+type BoundStateSyncSpecs = {
+  +specsPerHashKey: { +[string]: BoundStateSyncSpec<mixed, mixed, mixed> },
+  +specPerInnerHashKey: { +[string]: BoundStateSyncSpec<mixed, mixed, mixed> },
+};
 const stateSyncSpecSelectors = values(stateSyncSpecs).map(
   spec => spec.selector,
 );
-const boundStateSyncSpecsSelector: AppState => {
-  specsPerHashKey: { +[string]: BoundStateSyncSpec<mixed, mixed, mixed> },
-  specPerInnerHashKey: { +[string]: BoundStateSyncSpec<mixed, mixed, mixed> },
-} =
+const boundStateSyncSpecsSelector: AppState => BoundStateSyncSpecs =
   // The FlowFixMe is needed because createSelector types require flow
   // to know the number of subselectors at compile time.
   // $FlowFixMe
@@ -76,7 +77,7 @@
   boundStateSyncSpecsSelector,
   currentCalendarQuery,
   (
-    { specsPerHashKey, specPerInnerHashKey },
+    boundStateSyncSpecs: BoundStateSyncSpecs,
     calendarQuery: (calendarActive: boolean) => CalendarQuery,
   ) => {
     return async (
@@ -90,6 +91,7 @@
       const serverRequestedPlatformDetails = serverRequests.some(
         request => request.type === serverRequestTypes.PLATFORM_DETAILS,
       );
+      const { specsPerHashKey, specPerInnerHashKey } = boundStateSyncSpecs;
       for (const serverRequest of serverRequests) {
         if (
           serverRequest.type === serverRequestTypes.PLATFORM &&
diff --git a/lib/selectors/thread-selectors.js b/lib/selectors/thread-selectors.js
--- a/lib/selectors/thread-selectors.js
+++ b/lib/selectors/thread-selectors.js
@@ -36,7 +36,7 @@
   threadIsPending,
   getPendingThreadID,
 } from '../shared/thread-utils.js';
-import type { ClientEmojiAvatar } from '../types/avatar-types';
+import type { ClientAvatar, ClientEmojiAvatar } from '../types/avatar-types';
 import type { EntryInfo } from '../types/entry-types.js';
 import type { MessageStore, RawMessageInfo } from '../types/message-types.js';
 import type { BaseAppState } from '../types/redux-types.js';
@@ -109,7 +109,7 @@
   (
     inputThreadIDs: ?$ReadOnlySet<string>,
     threadInfos: $ReadOnlyArray<ThreadInfo>,
-  ) => {
+  ): $ReadOnlyArray<ThreadInfo> => {
     const threadIDs = inputThreadIDs;
     if (!threadIDs) {
       return threadInfos;
@@ -122,7 +122,7 @@
   state: BaseAppState<>,
 ) => $ReadOnlyArray<ThreadInfo> = createSelector(
   onScreenThreadInfos,
-  (threadInfos: $ReadOnlyArray<ThreadInfo>) =>
+  (threadInfos: $ReadOnlyArray<ThreadInfo>): $ReadOnlyArray<ThreadInfo> =>
     threadInfos.filter(threadInfo =>
       threadHasPermission(threadInfo, threadPermissions.EDIT_ENTRIES),
     ),
@@ -289,7 +289,9 @@
     ).length,
 );
 
-const baseAncestorThreadInfos = (threadID: string) =>
+const baseAncestorThreadInfos: (
+  threadID: string,
+) => (BaseAppState<>) => $ReadOnlyArray<ThreadInfo> = (threadID: string) =>
   createSelector(
     (state: BaseAppState<>) => threadInfoSelector(state),
     (threadInfos: {
@@ -312,7 +314,9 @@
   baseAncestorThreadInfos,
 );
 
-const baseOtherUsersButNoOtherAdmins = (threadID: string) =>
+const baseOtherUsersButNoOtherAdmins: (
+  threadID: string,
+) => (BaseAppState<>) => boolean = (threadID: string) =>
   createSelector(
     (state: BaseAppState<>) => state.threadStore.threadInfos[threadID],
     relativeMemberInfoSelectorForMembersOfThread(threadID),
@@ -443,7 +447,10 @@
   },
 );
 
-const baseSavedEmojiAvatarSelectorForThread = (
+const baseSavedEmojiAvatarSelectorForThread: (
+  threadID: string,
+  containingThreadID: ?string,
+) => (BaseAppState<>) => () => ClientAvatar = (
   threadID: string,
   containingThreadID: ?string,
 ) =>
@@ -469,7 +476,11 @@
   baseSavedEmojiAvatarSelectorForThread,
 );
 
-const baseThreadInfosSelectorForThreadType = (threadType: ThreadType) =>
+const baseThreadInfosSelectorForThreadType: (
+  threadType: ThreadType,
+) => (BaseAppState<>) => $ReadOnlyArray<ThreadInfo> = (
+  threadType: ThreadType,
+) =>
   createSelector(
     (state: BaseAppState<>) => threadInfoSelector(state),
     (threadInfos: {
diff --git a/lib/selectors/user-selectors.js b/lib/selectors/user-selectors.js
--- a/lib/selectors/user-selectors.js
+++ b/lib/selectors/user-selectors.js
@@ -17,6 +17,7 @@
 import {
   type RawThreadInfo,
   type RelativeMemberInfo,
+  type RawThreadInfos,
 } from '../types/thread-types.js';
 import type {
   UserInfos,
@@ -95,7 +96,9 @@
 const emptyArray: $ReadOnlyArray<RelativeMemberInfo> = [];
 
 // Includes current user at the start
-const baseRelativeMemberInfoSelectorForMembersOfThread = (
+const baseRelativeMemberInfoSelectorForMembersOfThread: (
+  threadID: ?string,
+) => (state: BaseAppState<>) => $ReadOnlyArray<RelativeMemberInfo> = (
   threadID: ?string,
 ) => {
   if (!threadID) {
@@ -204,9 +207,9 @@
 const usersWithPersonalThreadSelector: (
   state: BaseAppState<>,
 ) => $ReadOnlySet<string> = createSelector(
-  state => state.currentUserInfo && state.currentUserInfo.id,
-  state => state.threadStore.threadInfos,
-  (viewerID, threadInfos) => {
+  (state: BaseAppState<>) => state.currentUserInfo && state.currentUserInfo.id,
+  (state: BaseAppState<>) => state.threadStore.threadInfos,
+  (viewerID: ?string, threadInfos: RawThreadInfos) => {
     const personalThreadMembers = new Set<string>();
 
     for (const threadID in threadInfos) {