Fix bmc default root pass

Signed-off-by: Ben Levi <belevi@nvidia.com>

Author: benle7

sonic_platform_base/bmc_base.py

@@ -417,4 +417,8 @@ def reset_root_password(self):
                 ret: An integer return code indicating success (0) or failure
                 msg: A string containing success message or error description
         """
-        return self._change_login_password(self._get_default_root_password(), BMCBase.ROOT_ACCOUNT)
+        default_root_password = self._get_default_root_password()
+        if not default_root_password:
+            logger.log_error("BMC root account default password not found")
+            return (RedfishClient.ERR_CODE_GENERIC_ERROR, "BMC root account default password not found")
+        return self._change_login_password(default_root_password, BMCBase.ROOT_ACCOUNT)