fix(osal): initialize Windows thread sync correctly (#6604)

src/osal/lv_windows.c

@@ -152,6 +152,7 @@ lv_result_t lv_thread_sync_init(lv_thread_sync_t * sync)
 
     InitializeCriticalSection(&sync->cs);
     InitializeConditionVariable(&sync->cv);
+    sync->v = false;
 
     return LV_RESULT_OK;
 }