libobs: Fix race when disconnecting raw video callbacks

[derrod]

Description

Ensures raw_active counter is only incremented/decremented if a callback was actually added/removed.

Motivation and Context

Fixes #11329

There is a race condition here where the encoder stopping due to failure will call remove_connection() from full_stop() and the output itself stopping will also call it from end_data_capture_thread(). This can result in the raw_active counter being decremented twice to -1, so that the next time an output is started the counter will be incremented to 0 (instead of 1), which is treated as inactive.

How Has This Been Tested?

Locally.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[DeeDeeG]

The fix works for me, thanks!

(To be sure, I compiled OBS without this change (revision fbf2ea1) and could reproduce the original issue #11329. Recompiled with this PR (revision 6b0dd0b) and the issue is gone, no hangs. 👍)

(With this PR/fix, OBS can start new recordings successfully, and can exit cleanly, even after an encoder times out while using Hybrid MP4.)