autocompletion popup gets stuck if user saves before popup shown

[kevinushey]

System details

RStudio Edition : Desktop
RStudio Version : v1.2.1139
OS Version      : macOS 10.14.1
R Version       : 3.5.1 patched

Steps to reproduce the problem

Trigger an as-you-type autocompletion by typing, for example:

Sys.wh<TAB>

Then, immediately (before the popup shows!) try saving the file with Cmd + S.

Describe the problem in detail

The generated popup becomes 'stuck', and cannot be dismissed.

Describe the behavior you expected

Saving the document should cancel any in-flight completion requests.