Handle empty charset= value in Content-Type header
Handle empty charset= value in Content-Type header

Fixes https://github.com/validator/validator/issues/301 Thanks @mstange

takenspc/validator,tripu/validator,validator/validator,tripu/validator,validator/validator,validator/validator,tripu/validator,tripu/validator,validator/validator,tripu/validator,takenspc/validator,takenspc/validator,takenspc/validator,validator/validator,takenspc/validator