优化一些细节

TZImagePickerController/TZImagePickerController/TZImageManager.m

@@ -626,10 +626,10 @@ static dispatch_once_t onceToken;
 }
 
 - (void)savePhotoWithImage:(UIImage *)image location:(CLLocation *)location completion:(void (^)(NSError *error))completion {
-    NSData *data = UIImageJPEGRepresentation(image, 0.9);
     if (iOS8Later) {
         [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
             if (iOS9Later) {
+                NSData *data = UIImageJPEGRepresentation(image, 0.9);
                 PHAssetResourceCreationOptions *options = [[PHAssetResourceCreationOptions alloc] init];
                 options.shouldMoveFile = YES;
                 PHAssetCreationRequest *request = [PHAssetCreationRequest creationRequestForAsset];