Fix for bug 292390 . Prevent crash in certutil with -P option and dbprefix omitted.

security/nss/cmd/certutil/certutil.c

@@ -2482,8 +2482,13 @@ secuCommandFlag certutil_options[] =
     }
 
     /*  -P certdb name prefix */
-    if (certutil.options[opt_DBPrefix].activated)
-	certPrefix = strdup(certutil.options[opt_DBPrefix].arg);
+    if (certutil.options[opt_DBPrefix].activated) {
+        if (certutil.options[opt_DBPrefix].arg) {
+            certPrefix = strdup(certutil.options[opt_DBPrefix].arg);
+        } else {
+            Usage(progName);
+        }
+    }
 
     /*  -q PQG file or curve name */
     if (certutil.options[opt_PQGFile].activated) {