fix(exam businessflowlogic): resolve issue where preparation doesn't trigger after entering exam

src/states/businessFlowMiddlewareLogic.ts

@@ -21,8 +21,9 @@ const businessFlowMiddlewareLogic: Middleware =
       `[businessFlowMiddleware] Current business flow is now: ${state.currentKey} ; Last key was: ${state.lastKey}`
     );
     //进入检查
-    if (currentKey === 'exam') {
+    if (action.payload === 'exam') {
       prepare();
+      return next(action);
     }
     if (isFromExamToView(action.payload, currentKey)) {
       //从检查进入图像处理，有可能是曝光导致的，怎么知道呢？看发生器状态