Fix for n/a update_to_tag

Related-Prod: PROD-36426

Change-Id: If5d07fe083ea0f1293fa45acf391d3926d4b2e11
diff --git a/tcp_tests/tests/system/test_mcp_update.py b/tcp_tests/tests/system/test_mcp_update.py
index e4c84ac..6556e5f 100644
--- a/tcp_tests/tests/system/test_mcp_update.py
+++ b/tcp_tests/tests/system/test_mcp_update.py
@@ -359,22 +359,23 @@
             "I@salt:master",
             "_param:jenkins_pipelines_branch")
         LOG.info(actual_piplines_version)
-        if actual_piplines_version != "refs/tags/{}".format(
-                update_to_tag):
-            reclass_actions.add_key(
-                'parameters._param.jenkins_pipelines_branch',
-                "refs/tags/{}".format(
-                    update_to_tag),
-                'cluster/*/infra/init.yml')
-            salt.run_state("I@jenkins:client and not I@salt:master",
-                           "saltutil.refresh_pillar")
-            salt_actions.enforce_state("I@jenkins:client:lib",
-                                       "jenkins.client.lib")
-            salt_actions.cmd_run("cfg01*",
-                                 "cd /srv/salt/reclass; git add -u && "
-                                 "git commit --allow-empty "
-                                 "-m 'use workaround for PROD-37068 "
-                                 "missing'")
+        if update_to_tag is not None:
+            if actual_piplines_version != "refs/tags/{}".format(
+                    update_to_tag):
+                reclass_actions.add_key(
+                    'parameters._param.jenkins_pipelines_branch',
+                    "refs/tags/{}".format(
+                        update_to_tag),
+                    'cluster/*/infra/init.yml')
+                salt.run_state("I@jenkins:client and not I@salt:master",
+                               "saltutil.refresh_pillar")
+                salt_actions.enforce_state("I@jenkins:client:lib",
+                                           "jenkins.client.lib")
+                salt_actions.cmd_run("cfg01*",
+                                     "cd /srv/salt/reclass; git add -u && "
+                                     "git commit --allow-empty "
+                                     "-m 'use workaround for PROD-37068 "
+                                     "missing'")
 
         # ############### Start 'Pre-upgrade verify' job (since 2019.2.17)#####
         show_step(5)