fix(esp_event): clear running_task before releasing mutex on tick timeout

When esp_event_loop_run() exited via the ticks-expired break path,
loop->running_task was left pointing to the current task handle.
Any subsequent trylock in esp_event_handler_unregister_with_internal()
would see a stale non-NULL running_task and take the wrong code path.

components/esp_event/esp_event.c

@@ -728,6 +728,7 @@ esp_err_t esp_event_loop_run(esp_event_loop_handle_t event_loop, TickType_t tick
             remaining_ticks -= end - marker;
             // If the ticks to run expired, return to the caller
             if (remaining_ticks <= 0) {
+                loop->running_task = NULL;
                 xSemaphoreGiveRecursive(loop->mutex);
                 break;
             } else {