Don't choke on degenerate polygons.

It's a bit late to be asserting during drawing.
We'd need to know how the object was created to
do anything about it.

common/gal/opengl/opengl_gal.cpp

@@ -1460,7 +1460,8 @@ void OPENGL_GAL::DrawPolygon( const SHAPE_POLY_SET& aPolySet, bool aStrokeTriang
 
 void OPENGL_GAL::DrawPolygon( const SHAPE_LINE_CHAIN& aPolygon )
 {
-    wxCHECK( aPolygon.PointCount() >= 2, /* void */ );
+    if( aPolygon.PointCount() < 2 )
+        return;
 
     const int                   pointCount = aPolygon.SegmentCount() + 1;
     std::unique_ptr<GLdouble[]> points( new GLdouble[3 * pointCount] );