Panic Error on Exif Data for Software

[lk33]

• When trying to retrieve size of an image,
  size,_ := bimg.NewImage(img).Size()
• In github.com/h2non/bimg/metadata.go,
  Metadata function tries to extract Software tag from image. Wherein an image had Software value starting with '('. This is not being handled at github.com/h2non/bimg/vips.go -> vipsExifStringTag -> vipsExifShort,
  Leads to panic with slice out of bound stack trace.
• Infact, this vipsExifShort is being used to extract lot of Exif data in Metadata function.

Kindly handle images with such metadata. In case there is a hard restriction, please serve an error to handle gracefully.