this._form is null or not an object
As the error clearly states that it is a JavaScript error, I started checking all of my JavaScript code.
At last I found the root cause to resolve the issue.
When you are trying to include the JavaScript files in the page header you have to include the closing </Script> tag.
Incorrect / Causing Error:
<script src="~/scripts/abcd.js" type="text/javascript"/>
Correct:
<script src="~/scripts/abcd.js" type="text/javascript"></script>
