Problem Description
On the Dependencies tab in Plan Configuration, if you want to search Child plan on its field, somehow Bamboo will automatcially add undefined as the Child plan. The undefined will go away after refreshing the page, however it makes impossible to search for Child Plan.

Steps to replicate

1. Install Fresh Bamboo 5.2
2. Add some plan, say more than one plan, and navigate to Plan Configuration
3. Go to Dependencies tab and search for Child Plan
4. Notice that the undefined will be added under the Child Plan and it's impossible to search if Bamboo contains a lot of plans

The workaround for Bamboo 5.2 is to replace the existing BambooInstall/atlassian-bamboo/widget/autocomplete-controls/bamboo/plandependencies/plan-dependency.js file with the attached file and restart Bamboo.