Contact list pull-down can exceed parent column width

As per screenshot attached, the contact list pull-down displayed on the left hand side of the Messages page can exceed the width of the column its in if the names of courses within it exceed the length of the column.

Is is fixed by adding a css rule to the theme to set the width to that of the parent column.

The only side effect is that if your screen isn't wide enough, you may not be able to read the full title of course(s) in the list when its selected. While selecting (the pull-down is clicked on) the full names should be visible as expected.

Note: pay not attention to the DB error in the screenshot, that's resolved by MDL-26607.