Fix the input string failing to validate when the "Hex Byte
String" input type is selected and either the user adds a 0x prefix or
the "Hex" box is checked (or both).
The latter failure was particularly troublesome because when "Hex Byte
String" is selected the "Hex" checkbox is disabled. Users would have to
switch to a data type that enabled the box, toggle it, then switch back
to "Hex Byte String" to fix it.
Fix these errors by not adding a prefix when the "Hex" box is checked,
and removing the "0x" prefix from the user's input if present.
0093ed1ac8