Just to confirm, you aren't seeing any domains listed in WHM > DNS Functions > Edit DNS Zone area? Because if you do see zones, but do not select or type a valid domain name, the input in the search box ("Search") will be taken as the zone name and you will receive an error, since it cannot find any zone by the name "Search" to return.
You simply need to select a zone or type in a domain. Now, if you aren't seeing any domains listed and that area itself is blank of domains to select, this would be a different issue.