clan-app: decode function arguments ahead of launching a thread.

If something goew wrong here we rather want to crash the app and get bug
reports.

pkgs/clan-app/clan_app/deps/webview/webview.py

@@ -68,12 +68,9 @@ class Webview:
         arg: int,
     ) -> None:
         op_key = op_key_bytes.decode()
-
-        def thread_task(stop_event: threading.Event) -> None:
-            try:
         args = json.loads(request_data.decode())
-
         log.debug(f"Calling {method_name}({args[0]})")
+
         # Initialize dataclasses from the payload
         reconciled_arguments = {}
         for k, v in args[0].items():
@@ -91,6 +88,8 @@ class Webview:
         # TODO: We could remove the wrapper in the MethodRegistry
         # and just call the method directly
 
+        def thread_task(stop_event: threading.Event) -> None:
+            try:
                 set_should_cancel(lambda: stop_event.is_set())
                 result = wrap_method(**reconciled_arguments)