Problem deleting custom entity from default solution

I am trying to delete a custom entity from my default solution and the entity isn't included in any of our custom solutions.
This custom entity was part of a custom solution that has since been deleted. Now when trying to delete this entity from the default solution I see the following error in ErrorDetails log:

<Message>System.Web.HttpUnhandledException: Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #B5C0852A</Message>

<ErrorCode>-2147220970</ErrorCode>

<Message>There should be at least one entity returned. Count: 0</Message>