Try to fix: pad editor: incorrect zoom scale of pad preview on some installs.

Fixes: lp:1670086
https://bugs.launchpad.net/kicad/+bug/1670086

pcbnew/dialogs/dialog_pad_properties.cpp

@@ -150,6 +150,10 @@ void DIALOG_PAD_PROPERTIES::OnInitDialog( wxInitDialogEvent& event )
 {
     m_PadNumCtrl->SetFocus();
     m_PadNumCtrl->SetSelection( -1, -1 );
+
+    // Needed on some WM to be sure the pad is redrawn according to the final size
+    // of the canvas, with the right zoom factor
+    redraw();
 }