T0ProcACK: fix a potential problem

" Apparently, the fuzzer found one more similar bug: T0ProcACK() can be
called with the |proc_len| parameter equal to -1, leading to
stack-buffer-overflow.

The stack trace is:

    #1 0x56eee7 in T0ProcACK /ssd/ccid/src/fuzzer/../commands.c:1988:3
    #2 0x56d1d1 in CmdXfrBlockCHAR_T0 /ssd/ccid/src/fuzzer/../commands.c:2253:20
    #3 0x5754cc in IFDHTransmitToICC /ssd/ccid/src/fuzzer/../ifdhandler.c:1403:17

and the T0ProcACK() call is made from this line:
https://salsa.debian.org/rousseau/CCID/-/blob/c122e4f38cc7d1ffdb1fc0cece49145930d4634a/src/commands.c#L2197

The negative |proc_len| is the result of this equation: |exp_len -
*rcv_len|, with exp_len=2, *rcv_len=3 in the found scenario. "

The problem has been found by an automatic buzzer, not by a real problem
in the field.

Thanks to Maksim Ivanov for the bug report

src/commands.c

@@ -1855,6 +1855,9 @@ static RESPONSECODE T0ProcACK(unsigned int reader_index,
 
  DEBUG_COMM2("Enter, is_rcv = %d", is_rcv);
 
+ if (proc_len < 0)
+ return IFD_COMMUNICATION_ERROR;
+
  if (is_rcv == 1)
  { /* Receiving mode */
  unsigned int remain_len;