FIX: in grdtrack, -Su+d+r gives 0 result (#8730)

* FIX: in `grdtrack`, output 0 when -S[l|L|u|U]

* DOC: fix "stacked_profile.txt" in grdtrack.rst

Author: Dengda98

doc/rst/source/grdtrack.rst

@@ -200,7 +200,7 @@ Optional Arguments
     values to all cross-profiles. **+d** : Append stack deviations to
     all cross-profiles. **+r** : Append data residuals (data - stack) to
     all cross-profiles. **+s**\ [*file*] : Save stacked profile to
-    *file* [grdtrack_stacked_profile.txt]. **+c**\ *fact* : Compute
+    *file* [stacked_profile.txt]. **+c**\ *fact* : Compute
     uncertainty envelope on stacked profile as ±\ *fact* \*\ *deviation* [2].
     **Notes**: (1) Deviations depend on *method* and are standard deviation (**a**), L1
     scale, i.e., 1.4826 \* median absolute deviation (MAD) (for **m** and **p**),

src/grdtrack.c

@@ -1020,9 +1020,10 @@ EXTERN_MSC int GMT_grdtrack (void *V_API, int mode, void *args) {
 						M->data[2+k*n_step][row] = stacked_dev[k];	/* The stacked deviation */
 						M->data[3+k*n_step][row] = stacked_lo[k];	/* The stacked low value */
 						M->data[4+k*n_step][row] = stacked_hi[k];	/* The stacked high value */
-						if (Ctrl->S.mode >= STACK_LOWER) continue;
-						M->data[5+k*n_step][row] = stacked_val[k] - Ctrl->S.factor * stacked_dev[k];	/* The low envelope value */
-						M->data[6+k*n_step][row] = stacked_val[k] + Ctrl->S.factor * stacked_dev[k];	/* The low envelope value */
+						if (Ctrl->S.mode < STACK_LOWER) {
+							M->data[5+k*n_step][row] = stacked_val[k] - Ctrl->S.factor * stacked_dev[k];	/* The low envelope value */
+							M->data[6+k*n_step][row] = stacked_val[k] + Ctrl->S.factor * stacked_dev[k];	/* The low envelope value */
+						} 
 						if (n_added_cols == 0) continue;	/* No modification to profile outputs requested */
 						for (seg = 0; seg < T->n_segments; seg++) {	/* For each segment to append to */
 							col_s = colx;	/* Start over at this column */