CONNECTIVITY_DATA::IsConnectedOnLayer(): fix crash in some cases.

Fix crash when a zone do not have filled areas on a given layer.

pcbnew/connectivity/connectivity_data.cpp

@@ -462,6 +462,9 @@ bool CONNECTIVITY_DATA::IsConnectedOnLayer( const BOARD_CONNECTED_ITEM *aItem, i
                     else if( CN_ZONE_LAYER* zoneLayer = dynamic_cast<CN_ZONE_LAYER*>( connected ) )
                     {
                         ZONE*                   zone = static_cast<ZONE*>( zoneLayer->Parent() );
+
+                        if( zone->GetFill( layer )->OutlineCount() )
+                        {
                             int                     idx = zoneLayer->SubpolyIndex();
                             const SHAPE_LINE_CHAIN& island = zone->GetFill( layer )->COutline( idx );
                             SHAPE_CIRCLE            flashing( via->GetCenter(), via->GetWidth() / 2 );
@@ -471,6 +474,7 @@ bool CONNECTIVITY_DATA::IsConnectedOnLayer( const BOARD_CONNECTED_ITEM *aItem, i
                                 if( !flashing.SHAPE::Collide( pt ) )
                                     return true;
                             }
+                        }
 
                         // If the entire island is inside the via's flashing then the via won't
                         // *actually* connect to anything *else* so don't consider it connected.