act_build: replace array_key_exists with isset()

public_html/deployment/pages/act_build.php

@@ -46,7 +46,7 @@ if (!array_key_exists("confirm", $aParams)) {
 
     $sRevison = false;
     $aRepodata = $oPrj->getRepoRevision(true);
-    if (array_key_exists("revision", $aRepodata)) {
+    if (isset($aRepodata["revision"])) {
         $sRevison = $aRepodata["revision"];
         if (
                 array_key_exists("revision", $aPhaseData2["onhold"]) && $aPhaseData2["onhold"]["revision"] == $sRevison