Summary:
When a spinbox with the number of rows loses focus, the value of this spinbox (i.e., the count of rows) is always reset to 1. Thus, it's impossible to create more then one row.
To fix this bug, we need to implement `valueFromText` function.
BUG: 419141
FIXED-IN: 5.18.4
Reviewers: ngraham, zzag, davidedmundson
Reviewed By: ngraham, davidedmundson
Subscribers: kwin
Tags: #kwin
Differential Revision: https://phabricator.kde.org/D28378