Fix copy/pasta from previous commit.

pcbnew/zone_settings.cpp

@@ -249,13 +249,15 @@ void ZONE_SETTINGS::SetupLayersList( wxDataViewListCtrl* aList, PCB_BASE_FRAME*
     // TODO: something in wxWidgets 3.1.x pads checkbox columns with extra space.  (It used to
     // also be that the width of the column would get set too wide (to 30), but that's patched in
     // our local wxWidgets fork.)
-    checkColSize += 30;
+    int checkColMargins = 40;
+#else
+    int checkColMargins = 0;
 #endif
 
     // You'd think the fact that m_layers is a list would encourage wxWidgets not to save room
     // for the tree expanders... but you'd be wrong.  Force indent to 0.
     aList->SetIndent( 0 );
-    aList->SetMinClientSize( wxSize( checkColSize + layerColSize,
+    aList->SetMinClientSize( wxSize( checkColSize + checkColMargins + layerColSize,
                                      aList->GetMinClientSize().y ) );
 
     checkColumn->SetWidth( checkColSize );