resolve potential deadlocks (#66)

A deadlock could occur if the save callback is called just before the frontend set functions are used.
Thus unlock() is necessary before setting current scene or transition.
(e.g. if start recording is activated just before using the above functions, as this apparently triggers a save() call)

src/headers/switcher-data-structs.hpp

@@ -99,7 +99,7 @@ struct SwitcherData {
 
 	std::deque<SceneTransition> sceneTransitions;
 	std::deque<DefaultSceneTransition> defaultSceneTransitions;
-	bool changedDefTransitionRecently = false;
+	bool checkedDefTransition = false;
 
 	std::deque<MediaSwitch> mediaSwitches;
 
@@ -154,10 +154,12 @@ struct SwitcherData {
 	bool sceneChangedDuringWait();
 	bool prioFuncsValid();
 	void writeSceneInfoToFile();
-	void setDefaultSceneTransitions();
 	void autoStopStreamAndRecording();
 	void autoStartStreamRecording();
 	bool checkPause();
+	void checkDefaultSceneTransitions(bool &match,
+					  OBSWeakSource &transition);
+	void setCurrentDefTransition(OBSWeakSource &transition);
 	void checkSceneSequence(bool &match, OBSWeakSource &scene,
 				OBSWeakSource &transition,
 				std::unique_lock<std::mutex> &lock);