Merge pull request #2974 from dreampiggy/fix_code_style

Fix the wrong value assignment for SDAnimatedImageView code on macOS, warning

SDWebImage/Core/SDAnimatedImageView.m

@@ -470,7 +470,7 @@
 // NSImageView use a subview. We need this subview's layer for actual rendering.
 // Why using this design may because of properties like `imageAlignment` and `imageScaling`, which it's not available for UIImageView.contentMode (it's impossible to align left and keep aspect ratio at the same time)
 - (NSView *)imageView {
-    NSImageView *imageView = imageView = objc_getAssociatedObject(self, SD_SEL_SPI(imageView));
+    NSImageView *imageView = objc_getAssociatedObject(self, SD_SEL_SPI(imageView));
     if (!imageView) {
         // macOS 10.14
         imageView = objc_getAssociatedObject(self, SD_SEL_SPI(imageSubview));