Fix SegFault in req.get_query() call

This would segfault if called after an middleware that called an asynchronous function

src/socketify/socketify.py

@@ -2489,25 +2489,18 @@ class AppRequest:
             return None
 
     def get_query(self, key):
-        if self._query:
+        if self._query is None:
-            return self._query.get(key, None)
+            # Cache the query parameters
             buffer = ffi.new("char**")
-
+            query_string_length = lib.uws_req_get_query_string(self.req, buffer)
-        if isinstance(key, str):
+            if query_string_length > 0:
-            key_data = key.encode("utf-8")
-        elif isinstance(key, bytes):
-            key_data = key
-        else:
-            key_data = self.app._json_serializer.dumps(key).encode("utf-8")
-
-        length = lib.uws_req_get_query(self.req, key_data, len(key_data), buffer)
                 buffer_address = ffi.addressof(buffer, 0)[0]
-        if buffer_address == ffi.NULL:
+                query_string = ffi.unpack(buffer_address, query_string_length).decode("utf-8")
-            return None
+                from urllib.parse import parse_qs
-        try:
+                self._query = parse_qs(query_string)
-            return ffi.unpack(buffer_address, length).decode("utf-8")
+            else:
-        except Exception:  # invalid utf-8
+                self._query = {}
-            return None
+        return self._query.get(key, None)
 
     def get_parameters(self):
         if self._params: