keystore: reset credentials when they are not valid

src/misc/keystore.c

@@ -156,8 +156,15 @@ find_closest_path(vlc_keystore_entry *p_entries, unsigned i_count,
 static bool
 is_credential_valid(vlc_credential *p_credential)
 {
-    return p_credential->psz_username && *p_credential->psz_username != '\0'
-        && p_credential->psz_password;
+    if (p_credential->psz_username && *p_credential->psz_username != '\0'
+     && p_credential->psz_password)
+        return true;
+    else
+    {
+        p_credential->psz_username = p_credential->psz_password = NULL;
+        return false;
+    }
+
 }
 
 /* Default port for each protocol */