[native] Fix encrypted media upload on Android
Summary: This addresses ENG-9015.
Test Plan:
Confirm that upload of .dat files on Android no longer triggers the following error:
'upload failed', [Error: Failed to upload blob: guessContentTypeFromName(file.name) must not be null], undefined, undefined
Reviewers: bartek
Reviewed By: bartek
Subscribers: tomek
Differential Revision: https://phab.comm.dev/D13040