Activation of the Change Management - Standard Change Catalog plugin throws an error on an instance with a task that is not flattened. The error does not prevent the plug-in from activating; it is just preventing one index from being applied.
Steps to Reproduce
Log in to an instance without task flattening.
Activate the Change Management - Standard Change Catalog plugin.
Note that activation stops at 13% or 14%. However, the plugin shows it is active (which it is).
No workaround needed - this error can be ignored.
Related Problem: PRB1239940