UI: Fix disabling "resize output to source"

This should always be disabled if video output is active.  Additionally,
the expression used to determine whether it should be enabled/disabled
was very unreadable.

UI/window-basic-main.cpp

@@ -4361,10 +4361,7 @@ void OBSBasic::CreateSourcePopupMenu(int idx, bool preview)
 		int width = obs_source_get_width(source);
 		int height = obs_source_get_height(source);
 
-		resizeOutput->setEnabled(!(ui->streamButton->isChecked() ||
-				ui->recordButton->isChecked() ||
-				(replayBufferButton &&
-				replayBufferButton->isChecked())));
+		resizeOutput->setEnabled(!obs_video_active());
 
 		if (width == 0 || height == 0)
 			resizeOutput->setEnabled(false);