Do you have any MVC controllers where Page data is used (for example: SiteMapBase.GetCurrentNode()).
If so - this is bug logged in our Feedback
portal, which is fixed in the latest internal build (8.0.5704.0) and you can upgrade your project to that version in order to resolve it.
If not the case, you can try on a backup copy of your project to remove the Search index folder (~/App_Data/Sitefinity/Search) and to reindex (or just recreate the index).
In case this do not helps, I would recommend you to open a support ticket in order to provide your project for further investigation.
I hope this information helps.
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