Pop Up error when clicking on Run Plan in Firefox browser for Bamboo 7.0.4

Issue Summary:
In Bamboo 7.0.4 and 7.1.4, we can see an error pop up message in Firefox browser when we click on Run Plan.

Steps to Reproduce:

1. Login to Bamboo in Firefox.
2. Navigate to any plan and click on Run Plan.

Expected Results:

1. There shouldn't be any error pop up message on clicking Run Plan.

Actual Results:

1. You will see an error pop up message saying - An unexpected error has occurred.
2. This is very intermittent and vanishes within 10 secs without doing anything. Also this is not observed in IE and Chrome.

Workaround:
Temporary work around: a plugin that needs to be added as an add-on in Bamboo. To do this,

A) For Bamboo 7.0.4:

1. Download this file: atlassian-bamboo-plugin-web-resources-7.0.4-PS-64012.jar
2. Navigate to the Administration section -> "Manage Apps"
3. Click on "upload app" and load the file you just downloaded.

B) For newer versions of Bamboo (7.0.5+):

1. Stop Bamboo
2. Go to <BAMBOO-INSTALL>/atlassian-bamboo/WEB-INF/atlassian-bundled-plugins/
3. Move the atlassian-bamboo-plugin-web-resources-7.1.4.jar out from this folder to another directory different from the Bamboo install one
4. Copy the atlassian-bamboo-plugin-web-resources-7.0.4-PS-64012.jar file to that folder (atlassian-bundled-plugins)
5. Start Bamboo