增加数组越界判断

GMBase/Classes/UIViewController+PushType.m

@@ -27,13 +27,16 @@
     objc_setAssociatedObject(self, @"gmSnapshot", snapshot, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
 }
 
-// TODO: wangyang 从 release 分支看一下此处的逻辑，查清此处应该怎么改
 - (void)popToPresentPreviousController {
     for (int index = 0; index < self.navigationController.viewControllers.count; index++) {
         UIViewController *controller = self.navigationController.viewControllers[index];
         if ([controller conformsToProtocol:@protocol(GMCustomNavigationAnimationProtocol)]) {
+            if (index - 1 >= 0) {
                 UIViewController *previewController = self.navigationController.viewControllers[index - 1];
                 [controller.navigationController popToViewController:previewController animated:YES];
+            } else {
+                [controller.navigationController popViewControllerAnimated:YES];
+            }
             return;
         }
     }