overlays: Don't close overlays when drawing selections.
overlays: Don't close overlays when drawing selections.

This fixes the following bug:
* Open the streams modal.
* Click and hold in the word "Streams" at the top.
* Move pointer up out of the modal.
* Release.
* Expected: Some text is selected, but nothing else happens.
* Actual: The modal disappears.

We use the same fix we use for this class of issue in other places:
checking for whether a range is selected, and if so, doing nothing.

hackerkid/zulip,rht/zulip,zulip/zulip,rht/zulip,punchagan/zulip,punchagan/zulip,punchagan/zulip,andersk/zulip,eeshangarg/zulip,hackerkid/zulip,punchagan/zulip,hackerkid/zulip,andersk/zulip,zulip/zulip,andersk/zulip,kou/zulip,eeshangarg/zulip,eeshangarg/zulip,eeshangarg/zulip,kou/zulip,andersk/zulip,rht/zulip,zulip/zulip,eeshangarg/zulip,eeshangarg/zulip,rht/zulip,andersk/zulip,eeshangarg/zulip,kou/zulip,zulip/zulip,hackerkid/zulip,punchagan/zulip,rht/zulip,zulip/zulip,hackerkid/zulip,rht/zulip,andersk/zulip,kou/zulip,andersk/zulip,hackerkid/zulip,zulip/zulip,punchagan/zulip,hackerkid/zulip,kou/zulip,kou/zulip,punchagan/zulip,kou/zulip,rht/zulip,zulip/zulip