Fix error handling on strdup

[frankmorgner]

I have reviewed all issues that were brought up by CodeQL. Unfortunately, almost everyone of them was a false positive. It seems that CodeQL doesn't understand it when we're correctly handling some error in the line of the following:

p = calloc(5);
if (p == NULL)
   LOG_FUNC_RETURN(card->ctx, SC_ERROR_OUT_OF_MEMORY);

Anyway, one CodeQL issue at least led me to harden some other error handling around the referenced code.

Checklist

• Documentation is added or updated
• New files have a LGPL 2.1 license statement
• PKCS#11 module is tested
• Windows minidriver is tested
• macOS tokend is tested

[Jakuje]

otherwise lgtm