Fix typo in kaas triggers

PRODX-14029

Change-Id: Id1ad2904d729fc6282277e67cb5a887fa956615b
diff --git a/src/com/mirantis/mk/KaasUtils.groovy b/src/com/mirantis/mk/KaasUtils.groovy
index 9f15076..0e9c335 100644
--- a/src/com/mirantis/mk/KaasUtils.groovy
+++ b/src/com/mirantis/mk/KaasUtils.groovy
@@ -100,7 +100,7 @@
     if (deployMatches.size() > 0) {
         // override child version when it set explicitly
         deployChild = true
-        customChildRelease = matches[0][0].split('child-deploy')[1].replaceAll(']', '').trim()
+        customChildRelease = deployMatches[0][0].split('child-deploy')[1].replaceAll(']', '').trim()
         common.warningMsg("Forced child deployment using custom release version ${customChildRelease}")
     }
     if (commitMsg ==~ /(?s).*\[byo-attach\].*/ || env.GERRIT_EVENT_COMMENT_TEXT ==~ /(?s).*byo-attach.*/) {