Currently the SimulateTwoColEditConflict SpecialPage can be loaded even if the TwoColConflict extension is not enabled as a beta feature which results in an empty SpecialPage.
Since there seems to be no clean way to prevent the SpecialPage to be loaded, we should at least display a message telling the user to enable the extension as a beta feature.

Suggestion for message:
This SpecialPage is part of the Two column edit conflict extension. In order to use it, please enable the extension in your [https://en.wikipedia.beta.wmflabs.org/wiki/Special:Preferences#mw-prefsection-betafeatures beta feature preferences].