Tighten up activeCell setter in completion handler.
Tighten up activeCell setter in completion handler.

jupyter/jupyterlab,TypeFox/jupyterlab,TypeFox/jupyterlab,TypeFox/jupyterlab,eskirk/jupyterlab,charnpreetsingh185/jupyterlab,eskirk/jupyterlab,jupyter/jupyterlab,jupyter/jupyterlab,charnpreetsingh185/jupyterlab,eskirk/jupyterlab,charnpreetsingh185/jupyterlab,eskirk/jupyterlab,charnpreetsingh185/jupyterlab,TypeFox/jupyterlab,charnpreetsingh185/jupyterlab,jupyter/jupyterlab,jupyter/jupyterlab,TypeFox/jupyterlab,eskirk/jupyterlab