Move ownership of listener cleanup to BOARD itself

Fixes https://gitlab.com/kicad/code/kicad/-/issues/19736

pcbnew/board.cpp

@@ -181,6 +181,9 @@ BOARD::~BOARD()
     // cause call chains that query the containers
     for( BOARD_ITEM* item : ownedItems )
         delete item;
+
+    // Remove any listeners
+    RemoveAllListeners();
 }
 
 

pcbnew/widgets/pcb_net_inspector_panel.cpp

@@ -86,9 +86,6 @@ PCB_NET_INSPECTOR_PANEL::~PCB_NET_INSPECTOR_PANEL()
 
     m_netsList->AssociateModel( nullptr );
 
-    if( m_brd != nullptr )
-        m_brd->RemoveListener( this );
-
     // Disconnect from board events
     m_frame->Unbind( EDA_EVT_UNITS_CHANGED, &PCB_NET_INSPECTOR_PANEL::onUnitsChanged, this );
 
@@ -865,7 +862,7 @@ void PCB_NET_INSPECTOR_PANEL::OnBoardChanged()
 {
     m_brd = m_frame->GetBoard();
 
-    if( m_brd != nullptr )
+    if( m_brd )
         m_brd->AddListener( this );
 
     m_board_loaded = true;