qcacld-3.0: Avoid NULL pointer access in apf read memory cb

Add a check to validate hdd adapter to avoid NULL pointer
dereference.

Change-Id: I06d883c213e10b620d8af3f61baaeb483b078bf1
CRs-Fixed: 2240482

core/hdd/src/wlan_hdd_apf.c

@@ -452,6 +452,8 @@ hdd_apf_read_memory_callback(void *hdd_context,
 	}
 
 	adapter = hdd_get_adapter_by_vdev(hdd_ctx, evt->vdev_id);
+	if (hdd_validate_adapter(adapter))
+		return;
 	context = &adapter->apf_context;
 
 	if (context->magic != APF_CONTEXT_MAGIC) {