Blank value in button slicer

Hi,

unfortunately neither of them is true. If that were the case, the dax query I shared in the screenshots would contain a number on the row with the blank value, right?
When I imported the tables locally into PBI, and then recreated the semantic model, all was fine. So the conclusion is this is related to the storage mode. This is MS Servicedesk explenation:
Basically they say it's related to the way slicers work together with directlake models. Their suggested solution is to use referential integrity, but I disagree that this is a solution, as it will hide potential mapping issues in the future.

Below their answer:

Analysis and Resolution:   

• You contacted Microsoft Power BI Support request for the issue where Blank value appears in slicer.
• You agreed on the same note and confirmed to close this ticket as you do not have any further questions/concerns.
• We initially joined over the screen call and discussed the issue as below.

After discussing the issue with my internal SMEs, they have shared the following information based on initial investigation.
 

This behavior is caused by how Direct Lake semantic models materialize metadata for slicer visuals.

In Direct Lake mode, the engine may internally surface an implicit blank member during slicer enumeration. This blank value:

• Does not necessarily correspond to an actual blank or unmapped row in the data
• Does not appear in DAX anti‑joins or relationship validation queries
• Can be introduced due to how OneLake / Delta metadata, string normalization, or internal relationship evaluation is handled at query time

Additionally, Button Slicers fully enumerate dimension members and are more likely to surface such internal blank members compared to dropdown slicers.

This behavior is specific to Direct Lake models and does not typically occur in Import (VertiPaq) models.

As per the details provided by them, I can coincidence the same with the issue you have experienced.

When in import mode we do not see any blanks appear in the Slicer Visuals.

Also below is a Microsoft community post similar to the issue and they have suggested to Select the referential integrity button when creating the relationship.
 

Solved: (Blank) in slicer - Microsoft Fabric Community

Assume Referential Integrity Setting in Power BI Desktop - Power BI | Microsoft Learn

• We followed up on the suggestions and you mentioned the workaround is not so ideal for your scenario and since it is an expected behaviour you gave closure confirmation on the same.