To resolve this issue, make sure that you update Final Cut Pro X to it's most current version.
Note: If you are actively working on a project, avoid updating Final Cut Pro X until you are finished with the project. Either complete the project in the version of Final Cut Pro X you are currently working in, or ensure that you have a current backup of your events, projects, and Final Cut Pro X. This is so you can revert to the previous state that your data and the application were in if updating or upgrading to the latest version of Final Cut Pro X does not address your issue.