Uploading invalid JSON crashes the application.

If a user uploads invalid JSON, either from the clipboard or from a file, the whole application crashes.
This could possibly be fixed in a number of ways, maybe by checking for valid JSON or by just using a try-catch.

Start by reproducing the crash with invalid JSON through both the clipboard and file-upload paths, then trace the entry points that parse the uploaded content. Confirm how valid input currently behaves and identify the existing error-handling path. Done means invalid JSON no longer crashes the application and the user receives an appropriate failure response.

Written by the indexing model from the issue text.