fixed: cannot manage revisions in version tag

docs/changelog/7.x.x.txt

@@ -10,6 +10,7 @@
  - fixed: dashboard not working due to using legacy ajax handlers
  - fixed: Calendar form element no longer shows up behind admin console.
  - fixed: Asset Manager can now change ranks again
+ - fixed: Cannot manage revisions in version tags.
 
 7.5.12
  - skipping this release

lib/WebGUI/Operation/VersionTag.pm

@@ -60,7 +60,9 @@ sub canApproveVersionTag {
     my $tag         = shift;
     my $user        = shift || $session->user;
     my $instance    = $tag->getWorkflowInstance;
+    return 0 unless $instance;
     my $activity    = $instance->getNextActivity;
+    return 0 unless $activity;
     
     # Check if this person is in one of the allowed groups
     my $groupToApprove  = $activity->can( 'getGroupToApprove' )