处理根据索引获取数据引起的崩溃问题

TZImagePickerController/TZImagePickerController/TZImageManager.m

@@ -224,10 +224,18 @@ static CGFloat TZScreenScale;
 }
 
 ///  Get asset at index 获得下标为index的单个照片
+///  if index beyond bounds, return nil in callback 果索引越界, 在回调中返回 nil
 - (void)getAssetFromFetchResult:(id)result atIndex:(NSInteger)index allowPickingVideo:(BOOL)allowPickingVideo allowPickingImage:(BOOL)allowPickingImage completion:(void (^)(TZAssetModel *))completion {
     if ([result isKindOfClass:[PHFetchResult class]]) {
         PHFetchResult *fetchResult = (PHFetchResult *)result;
-        PHAsset *asset = fetchResult[index];
+        PHAsset *asset;
+        @try {
+            asset = fetchResult[index];
+        }
+        @catch (NSException* e) {
+            if (completion) completion(nil);
+            return;
+        }
         
         TZAssetModelMediaType type = TZAssetModelMediaTypePhoto;
         if (asset.mediaType == PHAssetMediaTypeVideo)      type = TZAssetModelMediaTypeVideo;
@@ -251,7 +259,12 @@ static CGFloat TZScreenScale;
             [group setAssetsFilter:[ALAssetsFilter allPhotos]];
         }
         NSIndexSet *indexSet = [NSIndexSet indexSetWithIndex:index];
+        
+        @try {
             [group enumerateAssetsAtIndexes:indexSet options:NSEnumerationConcurrent usingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) {
+                
+                if (!result) return;
+                
                 TZAssetModel *model;
                 TZAssetModelMediaType type = TZAssetModelMediaTypePhoto;
                 if (!allowPickingVideo){
@@ -271,6 +284,11 @@ static CGFloat TZScreenScale;
                 }
                 if (completion) completion(model);
             }];
+
+        }
+        @catch (NSException* e) {
+            if (completion) completion(nil);
+        }
     }
 }