Added missing check for returning an image with zero columns or rows (https://github.com/ImageMagick/ImageMagick/security/advisories/GHSA-8pj9-6897-74xc)

coders/dcm.c

@@ -4376,6 +4376,8 @@ static Image *ReadDCMImage(const ImageInfo *image_info,ExceptionInfo *exception)
   RelinquishDCMMemory(&info,&map,stream_info,stack,data);
   if (image == (Image *) NULL)
     return(image);
+  if ((image->rows == 0) || (image->columns == 0))
+    ThrowReaderException(CorruptImageError,"ImproperImageHeader")
   if (CloseBlob(image) == MagickFalse)
     status=MagickFalse;
   if (status == MagickFalse)