Vijay K - thanks for filing this
I noticed that you've mentioned running "Jenkins 2.7.4." Is that correct? Because, if so, I bet that's why stuff isn't working for you. I took a look at the plugin's pom.xml file, and it specifies a minimum Jenkins version of 2.60.3, here, on L54.
Are you able to move to a more up to date version of Jenkins itself? I'd recommend doing so anyway. Lots and lots of enhancements have gone in since 2.7.4, including a whole bunch of security enhancements that would be good to pick up.
In any event, I can't recreate it either.
Here it is running locally on my laptop, by building the plugin at the cloudbees-bitbucket-branch-source-2.4.0 tag, and running it in development mode via mvn hpi:run. That ends me up with Jenkins core 2.60.3:
I've also installed it to my more traditional system, which is running core 2.160 along with various beta-level plugins from the experimental update center: