Segmentation fault during PC/SC reader selection

### Steps to reproduce - have a PC/SC reader at slot `0` - set `LPAC_APDU_PCSC_DRV_IFID` to 1 or higher - do not set `LPAC_APDU_PCSC_DRV_NAME` - run `lpac chip info` ### Cause In [`driver/apdu/pcsc.c -> pcsc_open_hCard_iter()`](https://github.com/estkme-group/lpac/blob/ce4abfaf75d24a4578c6423cf7a833b1ecc55300/driver/apdu/pcsc.c#L120) when the current reader index does not match `LPAC_APDU_PCSC_DRV_IFID`, `LPAC_APDU_PCSC_DRV_NAME` is read but the code does not check if `getenv()` returns null. ### Fix A quick fix would be to check the nulllity: ```C const int id = getenv_or_default(ENV_DRV_IFID, (int)-1); if (id != -1 && id != index) { const char *part_name = getenv(ENV_DRV_NAME); if (part_name == NULL || strstr(reader, part_name) == NULL) { return 0; } } ``` However the current reader selection logic is a bit strange. `LPAC_APDU_PCSC_DRV_NAME` is only read if `LPAC_APDU_PCSC_DRV_IFID` is set (but at that point why?). I find either of these more intuitive: - `LPAC_APDU_PCSC_DRV_IFID` and `LPAC_APDU_PCSC_DRV_NAME` act independently (whichever matches first, selects the reader) ```C const int id = getenv_or_default(ENV_DRV_IFID, (int)-1); const char *part_name = getenv(ENV_DRV_NAME); if ((id != -1 || part_name != NULL) && // some of the positive filter env vars are set (id == -1 || id != index) && // DRV_IFID does not match (part_name == NULL || strstr(reader, part_name) == NULL) // DRV_NAME does not match ) { return 0; // reject the reader } ``` - `LPAC_APDU_PCSC_DRV_IFID` overrides `LPAC_APDU_PCSC_DRV_NAME` (i.e. the latter is ignored if the former is set) ```C const int id = getenv_or_default(ENV_DRV_IFID, (int)-1); const char *part_name = getenv(ENV_DRV_NAME); if ((id != -1 && id != index) || // DRV_IFID does not match (id == -1 && part_name != NULL && strstr(reader, part_name) == NULL) // DRV_IFID is not set and DRV_NAME does not match ) { return 0; // reject the reader } ```