fix(ble): remove null pointer assert in npl event deinit

Author: Zhou Xiao

components/bt/porting/npl/freertos/src/npl_os_freertos.c

@@ -110,7 +110,9 @@ IRAM_ATTR npl_freertos_event_init(struct ble_npl_event *ev, ble_npl_event_fn *fn
 void
 IRAM_ATTR npl_freertos_event_deinit(struct ble_npl_event *ev)
 {
-    BLE_LL_ASSERT(ev->event);
+    if (!ev->event) {
+        return;
+    }
 #if OS_MEM_ALLOC
     os_memblock_put(&ble_freertos_ev_pool,ev->event);
 #else