Resizer module should provide better information for error condition

[redmunds]

As described in this Brackets-Dev discussion thread, the message "Preference key 'undefined' must be a string" is not very helpful.

The problem is that Resizer expects an id on panel, so a simple fix would be for Resizer to verify panel has an id and otherwise display a message in console.

Note that this condition will most likely only affect Extension Authors while developing a new panel, so a console message should be sufficient feedback.

[peterflynn]

I have a fix locally

[TVScoundrel]

@peterflynn Will you implement the fix or is this still open for beginners like myself?

[peterflynn]

I've added a warning for this to PR #7264, along with improved docs indicating that an id is actually required

[peterflynn]

Oops, FBNC @redmunds -- the PR landed last sprint.

[redmunds]

Confirmed. Closing.