Fix NumberformatException message in hexCharToValue

The Misc.hex2Bytes function makes use of the hexCharToValue function, which limits character values to the numbers 0-9, capital A-F, and lowercase a-f. However, the NumberFormatException thrown for values outside of this range has the message "Hex character must be 0-9, a-z, or A-Z, but was ". This should be "Hex character must be 0-9, a-f, or A-F, but was ".