Beta MP's DataFlash viewer hides all data when Column is selected and then cancelled

On the latest Beta MP dataflash viewer, all the data in the data table is hidden if the user does this:

- open a .bin log file
- click on the column header to show a list of possible messages to filter by
- hit the Cancel button

The only way to make the data appear again is to uncheck/check the "Data Table" checkbox

EDIT: it seems actually that even selecting a message and pressing OK has the same effect. So just seems like the filtering by message feature is completely broken.

Reproduce the issue in the Beta Mission Planner DataFlash viewer using a .bin log, then trace the column-header message filtering flow for Cancel and OK. Done means filtering or cancelling no longer hides all rows, without needing to toggle the Data Table checkbox.

Written by the indexing model from the issue text.