Fix coverity uninitialized member warnings

Author: nyalldawson

src/app/qgsattributeactiondialog.cpp

@@ -235,6 +235,7 @@ QString QgsAttributeActionDialog::textForType( QgsAction::ActionType type )
     case QgsAction::OpenUrl:
       return tr( "Open URL" );
   }
+  return QString();
 }
 
 void QgsAttributeActionDialog::remove()

src/core/qgsattributetableconfig.cpp

@@ -18,6 +18,7 @@
 #include <QStringList>
 
 QgsAttributeTableConfig::QgsAttributeTableConfig()
+    : mActionWidgetStyle( DropDown )
 {
 
 }

src/gui/attributetable/qgsattributetableview.cpp

@@ -43,6 +43,7 @@ QgsAttributeTableView::QgsAttributeTableView( QWidget *parent )
     , mActionPopup( nullptr )
     , mRowSectionAnchor( 0 )
     , mCtrlDragSelectionFlag( QItemSelectionModel::Select )
+    , mActionWidget( nullptr )
 {
   QSettings settings;
   restoreGeometry( settings.value( "/BetterAttributeTable/geometry" ).toByteArray() );