fix xts case error for musl

Signed-off-by: Nyygxr <wuhao30@huawei.com>

multimedia/camera/camera_js_standard/src/main/ets/MainAbility/test/CameraJSUnitOutput.test.ets

@@ -781,6 +781,7 @@ export default function cameraJSUnitOutput(surfaceId: any) {
         console.info(TAG + "Entering SUB_MULTIMEDIA_CAMERA_CAPTURE_SESSION_ADD_METADATA_OUTPUT_CALLBACK_0100 captureSession == null || undefined")
         expect().assertFail();
       } else {
+        if (!isEmpty(metadataOutput)) {
           captureSession.addOutput(metadataOutput, async (err) => {
             if (!err) {
               expect(true).assertTrue();
@@ -794,6 +795,8 @@ export default function cameraJSUnitOutput(surfaceId: any) {
             done();
           })
         }
+        
+      }
       await sleep(1000);
       done();
     })