Fix \mb_convert_encoding error handling

[mateuszorzechowski]

Error thrown during converting value encoding from specified in VCF file to UTF-8 should be caught, but it is not, becouse since PHP 8.0.0 \mb_convert_encoding() will throw \ValueError (as mentioned in mb-convert-encoding-changelog) which inherits from \Error, which inherits directly from \Throwable, not \Exception which VCardParser is curently catching.

Currently VCF:

BEGIN:VCARD
...
N;CHARSET=windows-1250:Jacobsen;Thies-Tillman;;;
...

will throw error: mb_convert_encoding(): Argument #3 ($from_encoding) contains invalid encoding "windows-1250"
which is not handled