structio.thread.run_coro now makes sure the event loop is running before submitting tasks

structio/thread.py

@@ -346,7 +346,7 @@ def run_coro(
         pass
     else:
         raise StructIOException("cannot be called from async context")
-    if not is_async_thread():
+    if not is_async_thread() or _storage.parent_loop.done():
         raise StructIOException("run_coro requires a running loop in another thread!")
     # Wake up the event loop if it's blocked in a call to select() or similar I/O routine
     _storage.coro_runner.wakeup()