[Discover] Wrong sort order with empty sort URL parameter

[timroes]

Since 7.12 there is a regression when the sort parameter of the application state (URL or saved object) is empty. By default Discover creates saved searches with an empty sort array unless the user sorts by something.

Since 7.12 opening one of those saved searches will lead into the table being sorted by _doc (or I assume the configured tiebreaker field), but still show a sorting indicator on the timestamp column. This is firstly a regression and also very confusing since it's not at all obvious to the user, that they'll need to "resort" the table by that field they already think it's sorted by.

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)