Added GAL_TYPE_NONE as an indicator of GAL uninitialized state.

common/drawpanel_gal.cpp

@@ -52,6 +52,7 @@ EDA_DRAW_PANEL_GAL::EDA_DRAW_PANEL_GAL( wxWindow* aParentWindow, wxWindowID aWin
     wxWindow( aParentWindow, aWindowId, aPosition, aSize )
 {
     m_gal        = NULL;
+    m_currentGal = GAL_TYPE_NONE;
     m_view       = NULL;
     m_painter    = NULL;
 
@@ -158,7 +159,6 @@ void EDA_DRAW_PANEL_GAL::SwitchBackend( GalType aGalType, bool aUseShaders )
     if( aGalType == m_currentGal && aUseShaders == m_useShaders && m_gal != NULL )
         return;
 
-    if( m_gal )
     delete m_gal;
 
     switch( aGalType )
@@ -171,6 +171,9 @@ void EDA_DRAW_PANEL_GAL::SwitchBackend( GalType aGalType, bool aUseShaders )
     case GAL_TYPE_CAIRO:
         m_gal = new KiGfx::CAIRO_GAL( this, this, this );
         break;
+
+    case GAL_TYPE_NONE:
+        return;
     }
 
     m_gal->SetWorldUnitLength( 1.0 / METRIC_UNIT_LENGTH * 2.54 );   // 1 inch in nanometers

include/class_drawpanel_gal.h

@@ -50,6 +50,7 @@ class EDA_DRAW_PANEL_GAL : public wxWindow
 {
 public:
     enum GalType {
+        GAL_TYPE_NONE,      ///< Not used
         GAL_TYPE_OPENGL,    ///< OpenGL implementation
         GAL_TYPE_CAIRO,     ///< Cairo implementation
     };