whtopic.js error

I inherited a RoboHelp project and realized instead of publishing the compiled project, they were simply copying any changed files to the server.  I began publishing the project and our software program began throwing an error related to the whtopic.js file.

Error: The value of the property 'onSetStartPage' is null or undefined, not a function object

URL points to the whtopic.js file contained in Web Help

The coder added the bold line to the code, which seemed to solve the problem.

  gsPPath=_getFullPath(_getPath(document.location.href),
_getPath(sPath));

if (typeof (onSetStartPage) != "undefined")

            onSetStartPage();

My first question, of course, would be, what causes the error and how did the code update fix it.  I also wanted to mention after reviewing WebHelp on the server, I noticed there are multiple instances of the whtopic.js file, as well as another instance of the WebHelp project nested in the original.  Would these be causing conflict?  I'm wondering if it would be safe to delete the entire Web Help project from the server and re-publish everything fresh to see if it corrects the issue.  If not, any suggestions?