Fix #268: search input now appears on image chooser after form
validation error
Merge branch '268-fix-image-chooser-disappearing-search-box' of https://github.com/mope/wagtail into mope-268-fix-image-chooser-disappearing-search-box
changelog entry for #269
Merge branch 'mope-268-fix-image-chooser-disappearing-search-box'