Fix Stretch/Skew error

[alberto-azserve]

JSPaint reports an error while trying to open "Stretch/Skew" dialog.

TypeError: Cannot read properties of null (reading 'toUpperCase')
    at $RowInput (https://jspaint.app/src/functions.js:3569:65)
    at image_stretch_and_skew (https://jspaint.app/src/functions.js:3581:20)
    at Object.action (https://jspaint.app/src/menus.js:631:20)
    at item_action (https://jspaint.app/lib/os-gui/MenuBar.js:892:12)
    at HTMLTableRowElement.<anonymous> (https://jspaint.app/lib/os-gui/MenuBar.js:915:7)
    at HTMLTableRowElement.<anonymous> (https://jspaint.app/lib/os-gui/MenuBar.js:909:14)

Steps to reproduce the error:

1. Open https://jspaint.app/
2. Make sure not to use English (eg Italian)
3. Click Image - Stretch/Skew