libc/unistd: getopt: add some NULL pointer checks

Signed-off-by: Juha Niskanen <juha.niskanen@haltian.com>

libs/libc/unistd/lib_getopt_common.c

@@ -24,6 +24,7 @@
 
 #include <nuttx/config.h>
 
+#include <assert.h>
 #include <stdbool.h>
 #include <string.h>
 
@@ -514,7 +515,7 @@ int getopt_common(int argc, FAR char * const argv[],
                * not think that the first interpretation is standard.
                */
 
-              else if (*(go->go_optptr + 1) != '\0')
+              else if (go->go_optptr == NULL || go->go_optptr[1] != '\0')
                 {
                   /* Skip over the unrecognized long option. */
 
@@ -542,6 +543,8 @@ int getopt_common(int argc, FAR char * const argv[],
                * (which could be another single character command).
                */
 
+              DEBUGASSERT(go->go_optptr != NULL);
+
               go->go_optopt = *go->go_optptr;
               go->go_optptr = NULL;
               go->go_optind++;
@@ -570,6 +573,8 @@ int getopt_common(int argc, FAR char * const argv[],
 
       /* Check if the option appears in 'optstring' */
 
+      DEBUGASSERT(go->go_optptr != NULL);
+
       optchar = strchr(optstring, *go->go_optptr);
       if (!optchar)
         {