Clean up non-null assertions in the codebase

[growabeard]

This is a sub-issue of the code improvements issue.

• heavy use of non-null assertions (!!) in the subclasses when setting up the keyboard view

This will probably be used for multiple PRs to clean up this issue, as it is a pretty pervasive problem throughout the codebase.

[growabeard]

@andrewtavis I don't know if this is what you were looking for, please clean up if you're looking for more info 😄