fix fd leak for webp coder

Signed-off-by: zhangji <[email protected]>
diff --git a/coders/webp.c b/coders/webp.c
index e994886..c6f7fad 100644
--- a/coders/webp.c
+++ b/coders/webp.c
@@ -366,6 +366,7 @@
   }
   WebPFreeDecBuffer(webp_image);
   stream=(unsigned char*) RelinquishMagickMemory(stream);
+  (void) CloseBlob(image);
   return(image);
 }
 #endif