add more checks against invalid viewports

fix crash when activating some of the toc items in the testcase of #176513 (still it would be nice to know why they are "void" items"...)

svn path=/trunk/KDE/kdegraphics/okular/; revision=890803

core/document.cpp

@@ -2370,6 +2370,12 @@ void Document::setViewportPage( int page, int excludeId, bool smoothMove )
 
 void Document::setViewport( const DocumentViewport & viewport, int excludeId, bool smoothMove )
 {
+    if ( !viewport.isValid() )
+    {
+        kDebug(OkularDebug) << "invalid viewport:" << viewport.toString();
+        return;
+    }
+
     // if already broadcasted, don't redo it
     DocumentViewport & oldViewport = *d->m_viewportIterator;
     // disabled by enrico on 2005-03-18 (less debug output)

ui/toc.cpp

@@ -112,7 +112,7 @@ void TOC::slotExecuted( const QModelIndex &index )
         Okular::GotoAction action( externalFileName, viewport );
         m_document->processAction( &action );
     }
-    else
+    else if ( viewport.isValid() )
     {
         m_document->setViewport( viewport );
     }