Fix some Coverity null derefence warnings

Author: nyalldawson

src/app/composer/qgscomposertablebackgroundcolorsdialog.cpp

@@ -73,13 +73,15 @@ void QgsComposerTableBackgroundColorsDialog::apply()
     composition->beginMultiFrameCommand( mComposerTable, tr( "Table background customisation" ), QgsComposerMultiFrameMergeCommand::TableCellStyle );
   }
 
-  Q_FOREACH ( QgsComposerTableV2::CellStyleGroup styleGroup, mCheckBoxMap.keys() )
+  QMap< QgsComposerTableV2::CellStyleGroup, QCheckBox* >::const_iterator checkBoxIt = mCheckBoxMap.constBegin();
+  for ( ; checkBoxIt != mCheckBoxMap.constEnd(); ++checkBoxIt )
   {
     QgsComposerTableStyle style;
-    style.enabled = mCheckBoxMap.value( styleGroup )->isChecked();
-    style.cellBackgroundColor = mColorButtonMap.value( styleGroup )->color();
+    style.enabled = checkBoxIt.value()->isChecked();
+    if ( QgsColorButton* button = mColorButtonMap.value( checkBoxIt.key() ) )
+      style.cellBackgroundColor = button->color();
 
-    mComposerTable->setCellStyle( styleGroup, style );
+    mComposerTable->setCellStyle( checkBoxIt.key(), style );
   }
 
   mComposerTable->setBackgroundColor( mDefaultColorButton->color() );

src/app/nodetool/qgsmaptoolnodetool.cpp

@@ -166,13 +166,14 @@ void QgsMapToolNodeTool::canvasMoveEvent( QgsMapMouseEvent* e )
       double deltaX = curPos.x() - pressPos.x();
       double deltaY = curPos.y() - pressPos.y();
 
-      Q_FOREACH ( QgsFeatureId fid, mMoveRubberBands.keys() )
+      QMap<QgsFeatureId, QgsGeometryRubberBand*>::const_iterator moveBandsIt = mMoveRubberBands.constBegin();
+      for ( ; moveBandsIt != mMoveRubberBands.constEnd(); ++moveBandsIt )
       {
         typedef QPair<QgsVertexId, QgsPointV2> MoveVertex;
-        Q_FOREACH ( const MoveVertex& pair, mMoveVertices[fid] )
+        Q_FOREACH ( const MoveVertex& pair, mMoveVertices[ moveBandsIt.key()] )
         {
           QgsPointV2 newPos( pair.second.x() + deltaX, pair.second.y() + deltaY );
-          mMoveRubberBands.value( fid )->moveVertex( pair.first, newPos );
+          moveBandsIt.value()->moveVertex( pair.first, newPos );
         }
       }
     }

src/app/qgsvectorlayerproperties.cpp

@@ -295,7 +295,10 @@ QgsVectorLayerProperties::QgsVectorLayerProperties(
 
   mLayersDependenciesTreeGroup.reset( QgsProject::instance()->layerTreeRoot()->clone() );
   QgsLayerTreeLayer* layer = mLayersDependenciesTreeGroup->findLayer( mLayer->id() );
-  layer->parent()->takeChild( layer );
+  if ( layer )
+  {
+    layer->parent()->takeChild( layer );
+  }
   mLayersDependenciesTreeModel.reset( new QgsLayerTreeModel( mLayersDependenciesTreeGroup.data() ) );
   // use visibility as selection
   mLayersDependenciesTreeModel->setFlag( QgsLayerTreeModel::AllowNodeChangeVisibility );

src/core/composer/qgscomposertablev2.cpp

@@ -142,8 +142,12 @@ bool QgsComposerTableV2::writeXml( QDomElement& elem, QDomDocument & doc, bool i
   {
     QString styleName = it.value();
     QDomElement styleElem = doc.createElement( styleName );
-    mCellStyles.value( it.key() )->writeXml( styleElem, doc );
-    stylesElem.appendChild( styleElem );
+    QgsComposerTableStyle* style = mCellStyles.value( it.key() );
+    if ( style )
+    {
+      style->writeXml( styleElem, doc );
+      stylesElem.appendChild( styleElem );
+    }
   }
   elem.appendChild( stylesElem );
 

src/core/symbology-ng/qgscptcityarchive.cpp

@@ -115,8 +115,8 @@ QString QgsCptCityArchive::baseDir( QString archiveName )
   // search for matching archive in the registry
   if ( archiveName.isNull() )
     archiveName = DEFAULT_CPTCITY_ARCHIVE;
-  if ( mArchiveRegistry.contains( archiveName ) )
-    return mArchiveRegistry.value( archiveName )->baseDir();
+  if ( QgsCptCityArchive* archive = mArchiveRegistry.value( archiveName, nullptr ) )
+    return archive->baseDir();
   else
     return defaultBaseDir();
 }