virtualcam-module: Update filter size immediately when used in OBS

Fixes a crash due to the previous output size being used when scaling
the frame.

plugins/win-dshow/virtualcam-module/virtualcam-filter.cpp

@@ -270,6 +270,11 @@ void VCamFilter::Frame(uint64_t ts)
 			   the format we present to match */
 			SetVideoFormat(GetVideoFormat(), new_obs_cx, new_obs_cy,
 				       new_obs_interval);
+
+			/* Update the new filter size immediately since we
+			   know it just changed above */
+			new_filter_cx = new_obs_cx;
+			new_filter_cy = new_obs_cy;
 		}
 
 		/* Re-initialize the main scaler to use the new resolution */