git-gui: Error on restoring defaults

Hi there,

When selecting “Restore Defaults” in the Options dialogue via the Edit -> Options menu the following application error is received:

window name "!paving" already exists in parent
    while executing
"ttk::frame $w.!paving"
    (procedure "pave_toplevel" line 4)
    invoked from within
"pave_toplevel ."
    (procedure "apply_config" line 37)
    invoked from within
"apply_config"
    (procedure "do_restore_defaults" line 14)
    invoked from within
"do_restore_defaults"
    invoked from within
".options_editor.buttons.restore invoke "
    invoked from within
".options_editor.buttons.restore instate !disabled { .options_editor.buttons.restore invoke } "
    invoked from within
".options_editor.buttons.restore instate pressed { .options_editor.buttons.restore state !pressed; .options_editor.buttons.restore instate !disabled { ..."
    (command bound to event)

Tested using Git Gui 0.21 as included with Git 2.13.2 x64 on Windows x64. Also tested on a Windows VM with a clean install of Git.

Kind regards, Samuel Leslie