Fix initial value of the Tree Filter Bar

[AxelRICHARD]

• I have checked that this bug has not yet been reported by someone else
• I have checked that this bug appears on Chrome
• I have specified the version :

• 2023.6.1

• I have specified my environment :

• All

Screenshots

Steps to reproduce

Insert "null" string value in the label of any tree item.

Expected behavior

No highlight of any kind if the filter bar is disabled.

Actual behavior

"Null" string values are highlighted whether the filter bar is enabled or not.