SwLayAction: there can be only one, so assert that

Requires tweaking the SwLayIdle code a bit, where an action is kept
alive a bit after it's done, which would trigger the assertion.

Change-Id: Ic5c8f90bc101b9d73cfde9691b2bbf405a001393

sw/source/core/layout/layact.cxx

@@ -300,6 +300,7 @@ SwLayAction::SwLayAction( SwRootFrm *pRt, SwViewImp *pI ) :
     // OD 14.04.2003 #106346# - init new flag <mbFormatCntntOnInterrupt>.
     mbFormatCntntOnInterrupt = false;
 
+    assert(!pImp->pLayAct); // there can be only one SwLayAction
     pImp->pLayAct = this;   // register there
 }
 
@@ -2169,11 +2170,15 @@ SwLayIdle::SwLayIdle( SwRootFrm *pRt, SwViewImp *pI ) :
             pSh = (SwViewShell*)pSh->GetNext();
         } while ( pSh != pImp->GetShell() );
 
+        bool bInterrupt(false);
+        {
             SwLayAction aAction( pRoot, pImp );
             aAction.SetInputType( VCL_INPUT_ANY );
             aAction.SetIdle( true );
             aAction.SetWaitAllowed( false );
             aAction.Action();
+            bInterrupt = aAction.IsInterrupt();
+        }
 
         // Further start/end actions only happen if there were paints started
         // somewhere or if the visibility of the CharRects has changed.
@@ -2263,7 +2268,7 @@ SwLayIdle::SwLayIdle( SwRootFrm *pRt, SwViewImp *pI ) :
             } while ( pSh != pImp->GetShell() );
         }
 
-        if ( !aAction.IsInterrupt() )
+        if (!bInterrupt)
         {
             if ( !DoIdleJob( WORD_COUNT, false ) )
                 if ( !DoIdleJob( SMART_TAGS, false ) )