"How do I get rid of 'Empty main heading' at the beginning of my index?"

Answer: "In version 6.0, If you switch View Modes from any View other than Sorted View into Sorted View, all empty records at the top of the index will be deleted automatically. So if you're already in Sorted View, just change to As Entered View and then back to Sorted View. Alternately, in either version 6.0 or version 5.1, you may select the blank record in the entry grid and then use Control-X to remove it."

Answer: At the risk of stating the obvious, note you can also get rid of 'Empty main heading' simply by typing into it.

Why does this happen?

Answer: The SKY Index data entry grid cannot have zero records. Its design requires that it always have at least one record. If you create a group that has no matching records, a blank record is created to satisfy this requirement. When you create a new index database, one blank record is created. If you don't use that record for your first entry, you will end up with an empty record in your index. As stated above, when you switch into Sorted View from any other view mode, SKY Index will automatically remove those empty records.