libobs: If filter size invalid, skip filter

This shouldn't happen anymore because crop was fixed, but if a filter
returns 0x0 size and is invalid it shouldn't stop the filter chain.
Instead, it should just be skipped.

libobs/obs-source.c

@@ -2424,6 +2424,11 @@ void obs_source_process_filter_begin(obs_source_t *filter,
 		return;
 	}
 
+	if (!cx || !cy) {
+		obs_source_skip_video_filter(filter);
+		return;
+	}
+
 	if (!filter->filter_texrender)
 		filter->filter_texrender = gs_texrender_create(format,
 				GS_ZS_NONE);