Filter GCN notices lacking sky map info from creating sky maps; fixes #383
This MR is to prevent the creation of external sky maps when the GCN notices contains no sky map information (effectively when all ra/dec/error are blank).
This MR includes a check to whether any of the sky map values (ra/dec/error) are non-zero in order to create a sky map.
An example of this error is here: https://gracedb.ligo.org/events/E388215/view/.
Note that the GCN notices themselves have zeros in these fields, so there may be no other obvious way to filter these out.
Edited by Brandon Piotrzkowski