improvements for hidden spacers animations

plasmoid/package/contents/ui/ParabolicManager.qml

@@ -379,6 +379,13 @@ Item {
         if (hasInternalSeparator || root.showWindowsOnlyFromLaunchers) {
             var i = tasksModel.count - 1;
 
+            //! in case the last task is in deleting phase
+            var task = icList.childAtIndex(i+1);
+
+            if (task) {
+                i = i + 1;
+            }
+
             while (i>=0) {
                 if (!taskIsSeparator(i) && !taskIsForcedHidden(i) ) {
                     return i;

plasmoid/package/contents/ui/task/TaskHiddenSpacer.qml

@@ -44,9 +44,9 @@ Item{
     //the flag !root.inActivityChange protects from this
     //and it is used later on Behaviors in order to not break
     //the activity change animations from removal/additions of tasks
+    //! && !root.inActivityChange (deprecated) in order to check if it is fixed
     property int separatorSpace: neighbourSeparator && !isSeparator
-                                 && !(parabolicManager.hasInternalSeparator && root.dragSource)
-                                 && !root.inActivityChange ? //fix for #846
+                                 && !(parabolicManager.hasInternalSeparator && root.dragSource) ?
                                      (2+root.iconMargin/2) : 0
 
     property bool rightSpacer: false