I get a notice on opening the Context form

I am noticing the same issue. Has there been any progress on this issue?

I fixed it by changing the offending line to:

    $form['#default_value'] = array_key_exists(0, $values) ? $values[0] : 0;

It doesn't even look like you need to explicitly define the #default_value for that form field. Deleting the code that sets that still allows the form to pick up the regex defined in an existing context_useragent condition, unless I'm missing something.

See attached patch.

Patch is good. No need to define the default value.
Please roll it into project.

Ping.

Checking in on getting this into a new release.

This is now committed. A new dev version with the change should show up soon.