Fix: Possible to add empty item to checklist.

Thanks to nztqa ! Closes #1103

CHANGELOG.md

@@ -7,6 +7,10 @@ This release adds the following new features:
 * [When finished input of checklist item, open new checklist
   item](https://github.com/wekan/wekan/pull/1099).
 
+and fixes the following bugs:
+
+* [Possible to add empty item to checklist](https://github.com/wekan/wekan/pull/1107).
+
 Thanks to GitHub users nztqa and zarnifoulette for their contributions!
 
 # v0.27 2017-06-28 Wekan release