QStringEncoder subclasses, while valid, return empty name with TIS-620

Seems that QStringDecoder & QStringEncoder miss to get a proper non-empty name set when otherwise successfully (isValid is true, encoing & decoding works as expected.) created for the encoding name "TIS-620".

Running the attached example yields:

decoder valid: true name: 
encoder valid: true name: 

Seems to work fine for other encoding names, e.g. "ISO-8859-7", "windows-1250", "IBM850". So far only "TIS-620" seen to get an empty name.