UI: Disable safe mode when --multi is used

(cherry picked from commit ba25bc65c9a93e8dca8d56f8fec87d59ea3e08da)

UI/obs-app.cpp

@@ -3319,6 +3319,7 @@ int main(int argc, char *argv[])
 	for (int i = 1; i < argc; i++) {
 		if (arg_is(argv[i], "--multi", "-m")) {
 			multi = true;
+			disable_shutdown_check = true;
 
 #if ALLOW_PORTABLE_MODE
 		} else if (arg_is(argv[i], "--portable", "-p")) {