fix: video input on both output and monitoring

src/forge.c

@@ -313,6 +313,10 @@ static bool init(const Parameters *params) {
   }
 
 #ifdef VIDEO_IN
+  if (params->output && params->monitor) {
+    window_use(window_output, &context);
+  }
+
   shaders_link_inputs(&program, &project, &video_captures,
                       init_params.video_buffers);
 #endif /* VIDEO_IN */