Merge pull request #3288 from jianhan-he/master

[iOS] fix image show error
diff --git a/ios/sdk/WeexSDK/Sources/Component/WXImageComponent.m b/ios/sdk/WeexSDK/Sources/Component/WXImageComponent.m
index b117791..08d3635 100644
--- a/ios/sdk/WeexSDK/Sources/Component/WXImageComponent.m
+++ b/ios/sdk/WeexSDK/Sources/Component/WXImageComponent.m
@@ -311,7 +311,7 @@
 - (void)didFinishDrawingLayer:(BOOL)success {
     if ([self isViewLoaded]) {
         UIImage *image = ((UIImageView *)self.view).image;
-        if (image && !_layer.contents) {
+        if (image) {
             _layer.contents = (id)(image.CGImage);
         }
     }