Make sure router tool passes events it doesn't handle.

Fixes undo/redo when router tool is active but not routing.

pcbnew/router/router_tool.cpp

@@ -1182,6 +1182,10 @@ int ROUTER_TOOL::MainLoop( const TOOL_EVENT& aEvent )
         {
             m_menu.ShowContextMenu( selection() );
         }
+        else
+        {
+            evt->SetPassEvent();
+        }
 
         if( m_cancelled )
         {
@@ -1252,6 +1256,10 @@ void ROUTER_TOOL::performDragging( int aMode )
 
             break;
         }
+        else
+        {
+            evt->SetPassEvent();
+        }
 
         handleCommonEvents( *evt );
     }