Steps to Reproduce:

1. Click on Insert > Gallery
2. Think "Oops, I meant to click on Transclusion".
3. Try to get out of there without having a gallery added to your page.

Actual Results:
Click the < button: it adds a nearly invisible empty gallery. Press the ESCape key: it adds a nearly inisible empty gallery. Click elsewhere: it adds a nearly invisible empty gallery.

Expected Results:
I expected a trash can, but I'd prefer an X of the universal "click here to cancel" variety.

Reproducible: Didn't try

Version: unspecified
Severity: normal