Multiple selection fails on windows for Tree and TreeTable

[mmikeyy]

the reason is that on line 47 of treetable.js, which follows:

this.selection = (!event.metaKey) ? [] : this.selection || [];

it is the variable metaKey, not event.metaKey that should be tested.

Multiple row selection works when line 47 is changed to

this.selection = (!metaKey) ? [] : this.selection || [];