Prior to this commit MapFont#getWidth() did not account for the 1px
spacing inserted by CraftMapCanvas#drawText().
This commit adds the consideration of the 1px spacing per character
while taking care to not consider the last character as it will not
have a 1px space behind it. This commit also ensures the method will
not check a 0-length String.
By: eueln <euelnd@gmail.com>