Property value shown as "nan" after value is erased and spinbox left empty

Test steps:

Create a project and add some item, e.g a rectangle to Form Editor

In property pane, erase the position x -value. spinbox should now be empty

Use tab key to move the cursor to position y spinbox

-> position x is showing value 'nan'. If cursor is set to x position spinbox, numbers can also be added after nan.