Sidebar width isn't wide enough for tab labels in Catalan

The sidebar appears not to be resized to accommodate all tab labels, as is seen when changing the locale to Catalan.

The width seems to be determined by the widest widget in the tabs, which is currently the two checkboxes side-by-side, "Spplit on words" and "Keep delimiter".

How can the sidebar be sized to have space for all tabs? No idea...