[Fix][repc] Don't generate empty slot arrays

This includes addressing an issue where push<Prop> slots were not
defined correctly in the SourceApiMap.

Change-Id: I3791051f26c59d2b2cd1431cf166913b73d5fcba
Reviewed-by: Continuous Integration (KDAB) <build@kdab.com>
Reviewed-by: Michael Brasser <michael.brasser@live.com>