r.horizon: add default value 0 for step

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@65619 15284696-431f-4ddb-bdfa-cd5b030d7da7

raster/r.horizon/main.c

@@ -207,6 +207,7 @@ int main(int argc, char *argv[])
     parm.step->key = "step";
     parm.step->type = TYPE_DOUBLE;
     parm.step->required = NO;
+    parm.step->answer = "0";
     parm.step->description =
 	_("Angle step size for multidirectional horizon [degrees]");
     parm.step->guisection = _("Input options");