wait for engine threads to stop before exiting

fishy/engine/common/IEngine.py

@@ -23,7 +23,7 @@ class IEngine:
         # 0 - off, 1 - running, 2 - quitting
         self.state = 0
         self.window = None
-        self.thread = None
+        self.thread: Thread = None
 
     @property
     def gui(self):
@@ -47,6 +47,10 @@ class IEngine:
         self.thread = Thread(target=self._crash_safe)
         self.thread.start()
 
+    def join(self):
+        if self.thread:
+            self.thread.join()
+
     def turn_off(self):
         """
         this method only signals the thread to close using start flag,

fishy/engine/common/event_handler.py

@@ -71,6 +71,8 @@ class EngineEventHandler(IEngineHandler):
         self.quit_me()
 
     def stop(self):
+        self.semi_fisher_engine.join()
+        self.full_fisher_engine.join()
         if self.update_flag:
             auto_update.update_now(self.to_version)