Fix strtol error checking

Signed-off-by: Simo Sorce <simo@redhat.com>
Reviewed-by: Robbie Harwood <rharwood@redhat.com>

Author: simo5

src/mod_auth_gssapi.c

@@ -1542,7 +1542,7 @@ static const char *mag_deleg_ccache_perms(cmd_parms *parms, void *mconfig,
         if (isdigit(*p)) {
             char *endptr;
             cfg->deleg_ccache_uid = strtol(p, &endptr, 0);
-            if (errno != 0 || endptr != '\0') {
+            if (errno != 0 || (endptr && *endptr != '\0')) {
                 ap_log_error(APLOG_MARK, APLOG_ERR, 0, parms->server,
                              "Invalid GssapiDelegCcachePerms uid value [%s]",
                              p);
@@ -1567,7 +1567,7 @@ static const char *mag_deleg_ccache_perms(cmd_parms *parms, void *mconfig,
         if (isdigit(*p)) {
             char *endptr;
             cfg->deleg_ccache_gid = strtol(p, &endptr, 0);
-            if (errno != 0 || endptr != '\0') {
+            if (errno != 0 || (endptr && *endptr != '\0')) {
                 ap_log_error(APLOG_MARK, APLOG_ERR, 0, parms->server,
                              "Invalid GssapiDelegCcachePerms gid value [%s]",
                              p);