After content migration for a recent project, we noticed that certain components were throwing errors on the page once content was migrated. Note that we were using GatherContent, a really nice tool to prepare content for migration while implementation of the Sitecore solution was in progress. GatherContent provides a nifty Sitecore module that can be installed to extract content from GatherContent and create content in Sitecore (with field mappings, hierarchy, and such also covered).
But back to the issue at hand. This was the relevant portion of the error that was being thrown (BTW, we use GlassMapper in our implementations):
As can be seen, the issue arose in the “ReplaceReference” method of the “ProtectedImageLinkRenderer” in the “RenderField” pipeline and it was because there was an empty <a> tag in the content. My initial thoughts were that GlassMapper had some issue with the content in the field, but looking through existing bug reports on GlassMapper’s GitHub page provided me the clue.
This likely was introduced somehow from the GatherContent import, through copy and paste operations or something similar. Removing the empty <a> tags from the content resolved the issue.
UPDATE: Sitecore also provided support for this issue and have a hotfix out for it. The issue has already been resolved in Sitecore 8 Update 5 onwards, but if you’re using a Sitecore version before that, the hotfix can be found here: https://sitecore.box.com/s/ge56nod5k5xxy0ldkjxxumagywu6x9zf. This means, of course, that you can leave the empty <a> tags and they will be handled by Sitecore, but I preferred to clean things up.