This can be caused by an event form part on the page that has the option marked to Include Additional Donations, but doesn't have a fund selected. Follow the steps below to update the event form part: 
  1. Log in to NetCommunity 
  2. Click Site Explorer > Parts
  3. Search for the event form part that is on the page with the error
  4. Click the pencil icon to edit the event form part 
  5. Click Options
    • If you want to remove the Additional Donations Option:
      1. Unmark the checkbox for Allow Additional Donations
    • If you want to keep the Additional Donations Option: 
      1. Enter a display name for the fund
      2. Click the binoculars icon to choose the fund
  6. Click the Save button