pcbnew: Prevent use of non-connected item in ratsnest

We need to be careful in the connectivity system to always use
dyn_cast/dynamic_cast and check the return when dealing with board
items.  Getting non-connected items will result in null nets when
propagated.

Fixes https://gitlab.com/kicad/code/kicad/issues/5082

pcbnew/connectivity/connectivity_algo.cpp

@@ -46,36 +46,36 @@ bool CN_CONNECTIVITY_ALGO::Remove( BOARD_ITEM* aItem )
     case PCB_MODULE_T:
         for( auto pad : static_cast<MODULE*>( aItem ) -> Pads() )
         {
-            m_itemMap[ static_cast<BOARD_CONNECTED_ITEM*>( pad ) ].MarkItemsAsInvalid();
-            m_itemMap.erase( static_cast<BOARD_CONNECTED_ITEM*>( pad ) );
+            m_itemMap[pad].MarkItemsAsInvalid();
+            m_itemMap.erase( pad );
         }
 
         m_itemList.SetDirty( true );
         break;
 
     case PCB_PAD_T:
-        m_itemMap[ static_cast<BOARD_CONNECTED_ITEM*>( aItem ) ].MarkItemsAsInvalid();
-        m_itemMap.erase( static_cast<BOARD_CONNECTED_ITEM*>( aItem ) );
+        m_itemMap[aItem].MarkItemsAsInvalid();
+        m_itemMap.erase( aItem );
         m_itemList.SetDirty( true );
         break;
 
     case PCB_TRACE_T:
     case PCB_ARC_T:
-        m_itemMap[ static_cast<BOARD_CONNECTED_ITEM*>( aItem ) ].MarkItemsAsInvalid();
-        m_itemMap.erase( static_cast<BOARD_CONNECTED_ITEM*>( aItem ) );
+        m_itemMap[aItem].MarkItemsAsInvalid();
+        m_itemMap.erase( aItem );
         m_itemList.SetDirty( true );
         break;
 
     case PCB_VIA_T:
-        m_itemMap[ static_cast<BOARD_CONNECTED_ITEM*>( aItem ) ].MarkItemsAsInvalid();
-        m_itemMap.erase( static_cast<BOARD_CONNECTED_ITEM*>( aItem ) );
+        m_itemMap[aItem].MarkItemsAsInvalid();
+        m_itemMap.erase( aItem );
         m_itemList.SetDirty( true );
         break;
 
     case PCB_ZONE_AREA_T:
     {
-        m_itemMap[ static_cast<BOARD_CONNECTED_ITEM*>( aItem ) ].MarkItemsAsInvalid();
-        m_itemMap.erase ( static_cast<BOARD_CONNECTED_ITEM*>( aItem ) );
+        m_itemMap[aItem].MarkItemsAsInvalid();
+        m_itemMap.erase ( aItem );
         m_itemList.SetDirty( true );
         break;
     }

pcbnew/connectivity/connectivity_data.cpp

@@ -213,7 +213,8 @@ void CONNECTIVITY_DATA::BlockRatsnestItems( const std::vector<BOARD_ITEM*>& aIte
         }
         else
         {
-            citems.push_back( static_cast<BOARD_CONNECTED_ITEM*>(item) );
+            if( auto citem = dynamic_cast<BOARD_CONNECTED_ITEM*>( item ) )
+                citems.push_back( citem );
         }
     }
 

pcbnew/tools/pcb_inspection_tool.cpp

@@ -183,10 +183,8 @@ int PCB_INSPECTION_TOOL::HighlightItem( const TOOL_EVENT& aEvent )
 
         for( auto item : selection )
         {
-            if( BOARD_CONNECTED_ITEM::ClassOf( item ) )
+            if( auto ci = dyn_cast<BOARD_CONNECTED_ITEM*>( item ) )
             {
-                auto ci = static_cast<BOARD_CONNECTED_ITEM*>( item );
-
                 int item_net = ci->GetNetCode();
 
                 if( net < 0 )
@@ -502,7 +500,10 @@ void PCB_INSPECTION_TOOL::calculateSelectionRatsnest()
 
     for( EDA_ITEM* item : selection )
     {
-        BOARD_CONNECTED_ITEM* boardItem = static_cast<BOARD_CONNECTED_ITEM*>( item );
+        BOARD_CONNECTED_ITEM* boardItem = dyn_cast<BOARD_CONNECTED_ITEM*>( item );
+
+        if( !boardItem )
+            continue;
 
         if( boardItem->Type() == PCB_MODULE_T )
         {