Equals condition doesn't work fine for no mandatory field

• Type: Bug
• Status: Closed
• Resolution: No Longer Reproducible
• Affects Version/s: 7.0.5 CE GA6
• Fix Version/s: 7.0.X, 7.1.0 CE GA1, 7.1.X, Master
• Component/s: Dynamic Data Mapping > Form Builder
• Labels: None
• Story Points: 2

I have three rows to declare three range interval:

Date 1 from *: _____________ Date 1 to *: _____________
Date 2 from : _____________ Date 2 to : _____________
Date 3 from : _____________ Date 3 to : _____________

Only the fields belong to first row are mandatory. The second and the third row are hidden and
their visibility is driven by this condition:

"Date 2 from" and "Date 2 to" visibility are driven by "NOT(equals(Date1To,""))". The rule is inserted into "Field Visibility Expression" during the definition of the fields into Form Builder View (Liferay Back Office).

When I compile che field "Date 1 to" the fields belong to second row are correctly display.

The visibility of the third line fields depends on "NOT(equals(Date2To,""))" condition, but when I compile "Date 2 to" field the third line doesn't compare.
If I set "Date 2 from" and "Date 2 to" fields as mandatory the previous condition works fine and the third line is showed when I fill the field "Date 2 to".