fix silent error in run_task (#2959)

* fix silent error in run_task

* fix

sdk/python/packages/flet-core/src/flet_core/page.py

@@ -495,7 +495,18 @@ def __on_page_change_event(self, data):
 
     def run_task(self, handler: Callable[..., Awaitable[Any]], *args, **kwargs):
         assert asyncio.iscoroutinefunction(handler)
-        return asyncio.run_coroutine_threadsafe(handler(*args, **kwargs), self.__loop)
+
+        future = asyncio.run_coroutine_threadsafe(handler(*args, **kwargs), self.__loop)
+
+        def _on_completion(f):
+            exception = f.exception()
+
+            if exception:
+                raise exception
+
+        future.add_done_callback(_on_completion)
+
+        return future
 
     def run_thread(self, handler, *args):
         if is_pyodide():