Reason
This issue occurs when a complex condition is created, and one of the sub conditions is deleted. In the case below, the correlation rule is missing a sub condition that would have been used together with the Rule Message condition, but it has been deleted. The following screenshot shows a similar situation.
Workaround
The workaround of this issue is to delete the "indented" broken complex condition, and adding it back to the rule as a regular condition.
