DataFlash viewer's message filter requires user to specifically select message

The Dataflash viewer's message filter acts upon the message selected from the drop-down instead of the string the user has typed in.

Below is a screen shot of the situation recreated on my desktop.

I've opened a log file (any log file will do), clicked the "Data Table" checkbox and clicked on the column headers row. The list of message types has appeared but instead of selecting with the mouse, I've typed in "GPS". The drop-down moves to where the "GPS" is shown in the list but if i then press "Enter" it filters by "AHR2" instead of "GPS".

Start in Mission Planner's Dataflash viewer and reproduce the issue by opening a log, enabling Data Table, opening the message-type list, typing "GPS," and pressing Enter. Trace the message filter's handling of typed text versus the selected drop-down item; done means Enter filters by GPS rather than the previously selected AHR2.

Written by the indexing model from the issue text.