Merge pull request #4 from wantedly/awakia/fix-iOS11.2

Fix for iOS11.2

Author: Yu Tawata

iOS-WebP/UIImage+WebP.m

@@ -159,7 +159,7 @@ + (UIImage *)imageWithWebPData:(NSData *)imgData error:(NSError **)error
 
     // Construct UIImage from the decoded RGBA value array
     uint8_t *data = WebPDecodeRGBA([imgData bytes], [imgData length], &width, &height);
-    CGDataProviderRef provider = CGDataProviderCreateWithData(config, data, config->options.scaled_width  * config->options.scaled_height * 4, free_image_data);
+    CGDataProviderRef provider = CGDataProviderCreateWithData(config, data, (config->options.scaled_width || width) * (config->options.scaled_height || height) * 4, free_image_data);
 
     CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
     CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault |kCGImageAlphaLast;