SdrModel: make sure undo/redo stacks are not empty

most probably Undo() does not get called if there is no undo actions,
just to be on the safe side.

Change-Id: I3597698dbe8208916be94ebddd7260fbd7eadc74

svx/inc/svx/svdmodel.hxx

@@ -575,13 +575,9 @@ public:
     void  SetMaxUndoActionCount(sal_uIntPtr nAnz);
     sal_uIntPtr GetMaxUndoActionCount() const { return nMaxUndoCount; }
     void  ClearUndoBuffer();
-    // UndoAction(0) ist die aktuelle (also die zuletzt eingegangene)
-    sal_uIntPtr GetUndoActionCount() const                      { return pUndoStack!=NULL ? pUndoStack->size() : 0; }
-    const SfxUndoAction* GetUndoAction(sal_uIntPtr nNum) const  { return (SfxUndoAction*)(pUndoStack!=NULL ? (*pUndoStack)[nNum] : NULL); }
-    // RedoAction(0) ist die aktuelle (also die des letzten Undo)
-    sal_uIntPtr GetRedoActionCount() const                      { return pRedoStack!=NULL ? pRedoStack->size() : 0; }
-    const SfxUndoAction* GetRedoAction(sal_uIntPtr nNum) const  { return (SfxUndoAction*)(pRedoStack!=NULL ? (*pRedoStack)[nNum] : NULL); }
 
+    bool HasUndoActions() const;
+    bool HasRedoActions() const;
     bool Undo();
     bool Redo();
     bool Repeat(SfxRepeatTarget&);

svx/source/dialog/imapdlg.cxx

@@ -791,8 +791,8 @@ IMPL_LINK( SvxIMapDlg, StateHdl, IMapWindow*, pWnd )
     aTbxIMapDlg1.EnableItem( TBI_POLYDELETE, !bDrawEnabled && pView->IsDeleteMarkedPointsPossible() );
 
     // Undo/Redo
-    aTbxIMapDlg1.EnableItem( TBI_UNDO, pModel->GetUndoActionCount() > 0 );
-    aTbxIMapDlg1.EnableItem( TBI_REDO, pModel->GetRedoActionCount() > 0 );
+    aTbxIMapDlg1.EnableItem( TBI_UNDO, pModel->HasUndoActions() );
+    aTbxIMapDlg1.EnableItem( TBI_REDO, pModel->HasRedoActions() );
 
     if ( bPolyEdit )
     {

svx/source/svdraw/svdmodel.cxx

@@ -431,6 +431,16 @@ void SdrModel::ClearUndoBuffer()
     }
 }
 
+bool SdrModel::HasUndoActions() const
+{
+    return pUndoStack && !pUndoStack->empty();
+}
+
+bool SdrModel::HasRedoActions() const
+{
+    return pRedoStack && !pRedoStack->empty();
+}
+
 bool SdrModel::Undo()
 {
     bool bRet = false;
@@ -440,7 +450,7 @@ bool SdrModel::Undo()
     }
     else
     {
-        SfxUndoAction* pDo=(SfxUndoAction*)GetUndoAction(0);
+        SfxUndoAction* pDo = HasUndoActions() ? pUndoStack->front() : NULL;
         if(pDo!=NULL)
         {
             const bool bWasUndoEnabled = mbUndoEnabled;
@@ -466,7 +476,7 @@ bool SdrModel::Redo()
     }
     else
     {
-        SfxUndoAction* pDo=(SfxUndoAction*)GetRedoAction(0);
+        SfxUndoAction* pDo = HasRedoActions() ? pRedoStack->front() : NULL;
         if(pDo!=NULL)
         {
             const bool bWasUndoEnabled = mbUndoEnabled;
@@ -492,7 +502,7 @@ bool SdrModel::Repeat(SfxRepeatTarget& rView)
     }
     else
     {
-        SfxUndoAction* pDo=(SfxUndoAction*)GetUndoAction(0);
+        SfxUndoAction* pDo = HasUndoActions() ? pUndoStack->front() : NULL;
         if(pDo!=NULL)
         {
             if(pDo->CanRepeat(rView))