res_geoloc: fix NULL pointer dereference bug

The `ast_geoloc_datastore_add_eprofile` function does not return 0 on
success, it returns the size of the underlying datastore. This means
that the datastore will be freed and its pointer set to NULL when no
error occured at all.

ASTERISK-30346

Change-Id: Iea9b209bd1244cc57b903b9496cb680c356e4bb9