predict-refine: Remove out-of-bounds GSL vector access

We got away with this because the GSL error handler is turned off in
indexamjig.c, and invalid accesses are defined to return 0.  However,
these accesses should have been removed when the clen refinement was
disabled in predict-refine

libcrystfel/src/predict-refine.c

@@ -540,10 +540,10 @@ static int iterate(struct reflpeak *rps, int n, UnitCell *cell,
 	csz += gsl_vector_get(shifts, 8);
 	update_detector(image->det, gsl_vector_get(shifts, 9),
 	                            gsl_vector_get(shifts, 10),
-	                            gsl_vector_get(shifts, 11));
+	                            0.0);
 	*total_x += gsl_vector_get(shifts, 9);
 	*total_y += gsl_vector_get(shifts, 10);
-	*total_z += gsl_vector_get(shifts, 11);
+	*total_z += 0.0;
 
 	cell_set_reciprocal(cell, asx, asy, asz, bsx, bsy, bsz, csx, csy, csz);