libobs: Fix cache overflowing (memory leak)

Fixes a bug where all frames in the cache would get marked as 'in use',
this causing it to continually allocate new frames continually.

libobs/obs-source.c

@@ -1392,6 +1392,7 @@ static inline struct obs_source_frame *cache_video(struct obs_source *source,
 		if (!af->used) {
 			new_frame = af->frame;
 			af->used = true;
+			break;
 		}
 	}