fix gcc maybe-uninitialized compiler warnings in acl_addr

fix gcc maybe-uninitialized compiler warnings in acl_addr

I can't tell if they're false positives or not, but compiling with
no warnings is better than seeing this:

filters.c: In function ‘acl_addr’:
filters.c:465:31: warning: ‘addr_len’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  465 |    for (i = 0; (i < addr_len) && masklength; i++)
      |                ~~~~~~~~~~~~~~~^~~~~~~~~~~~~
filters.c:454:18: warning: ‘mask_port’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  454 |       *mask_port = 1;
      |       ~~~~~~~~~~~^~~
filters.c:479:19: warning: ‘mask_data’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  479 |          mask_data[i] = (uint8_t)~((1 << (8 - masklength)) - 1);
      |                   ^