the GV's name can be NULL.
p4raw-id: //depot/perl@30439
#define GvLINE(gv) (GvGP(gv)->gp_line)
#define GvFILE_HEK(gv) (GvGP(gv)->gp_file_hek)
-#define GvFILE(gv) HEK_KEY(GvFILE_HEK(gv))
+#define GvFILE(gv) (GvFILE_HEK(gv) ? HEK_KEY(GvFILE_HEK(gv)) : NULL)
#define GvFILEGV(gv) (gv_fetchfile(GvFILE(gv)))
#define GvEGV(gv) (GvGP(gv)->gp_egv)