diff --git a/lib/permissions/permissionutil.inc.php b/lib/permissions/permissionutil.inc.php
index 30517d2..da1aa83 100644
--- a/lib/permissions/permissionutil.inc.php
+++ b/lib/permissions/permissionutil.inc.php
@@ -249,21 +249,23 @@ class KTPermissionUtil {
 
         if (!is_a($oFolderOrDocument, 'Folder')) {
             $oState = KTWorkflowUtil::getWorkflowStateForDocument($oFolderOrDocument);
-            $aWorkflowStatePermissionAssignments = KTWorkflowStatePermissionAssignment::getByState($oState);
-            foreach ($aWorkflowStatePermissionAssignments as $oAssignment) {
-                $iPermissionId = $oAssignment->getPermissionId();
-                $iPermissionDescriptorId = $oAssignment->getDescriptorId();
-
-                $oPD = KTPermissionDescriptor::get($iPermissionDescriptorId);
-                $aGroupIDs = $oPD->getGroups();
-                $aUserIDs = array();
-                $aRoleIDs = $oPD->getRoles();
-                $aAllowed = array(
-                    "group" => $aGroupIDs,
-                    "user" => $aUserIDs,
-                    "role" => $aRoleIDs,
-                );
-                $aMapPermAllowed[$iPermissionId] = $aAllowed;
+            if (!(PEAR::isError($oState) || is_null($oState) || ($oState == false))) {
+                $aWorkflowStatePermissionAssignments = KTWorkflowStatePermissionAssignment::getByState($oState);
+                foreach ($aWorkflowStatePermissionAssignments as $oAssignment) {
+                    $iPermissionId = $oAssignment->getPermissionId();
+                    $iPermissionDescriptorId = $oAssignment->getDescriptorId();
+                    
+                    $oPD = KTPermissionDescriptor::get($iPermissionDescriptorId);
+                    $aGroupIDs = $oPD->getGroups();
+                    $aUserIDs = array();
+                    $aRoleIDs = $oPD->getRoles();
+                    $aAllowed = array(
+                        "group" => $aGroupIDs,
+                        "user" => $aUserIDs,
+                        "role" => $aRoleIDs,
+                    );
+                    $aMapPermAllowed[$iPermissionId] = $aAllowed;
+                }
             }
         }
 
diff --git a/templates/kt3/document/metadata_history.smarty b/templates/kt3/document/metadata_history.smarty
index 96fb5a6..8b913e1 100644
--- a/templates/kt3/document/metadata_history.smarty
+++ b/templates/kt3/document/metadata_history.smarty
@@ -30,7 +30,13 @@
                    <a href="{addQS}action=viewComparison&fDocumentId={$document->getId()}&fBaseVersion={$oVersion->getMetadataVersionId()}&fComparisonVersion={$oVersion->getCurrentMetadataVersionId()}{/addQS}">{i18n}compare with current{/i18n}</a></td>                
                 {/if}
                 </td>     
-                <td><a href="{addQS}action=startComparison&fDocumentId={$document->getId()}&fComparisonVersion={$oVersion->getCurrentMetadataVersionId()}{/addQS}">{i18n}compare with other version{/i18n}</a></td>
+                <td>
+                {if (count($versions) == 1)}
+                &mdash;
+                {else}
+                <a href="{addQS}action=startComparison&fDocumentId={$document->getId()}&fComparisonVersion={$oVersion->getCurrentMetadataVersionId()}{/addQS}">{i18n}compare with other version{/i18n}</a>
+                {/if}
+                </td>
             </tr>
             {/foreach}
         </tbody>