Patch for issue #22818 (#23170)

When calling "differential_drive stop" a missing return statement was causing a segmentation fault due to access to already freed memory.

src/modules/differential_drive/DifferentialDrive.cpp

@@ -66,6 +66,7 @@ void DifferentialDrive::Run()
 	if (should_exit()) {
 		ScheduleClear();
 		exit_and_cleanup();
+		return;
 	}
 
 	hrt_abstime now = hrt_absolute_time();