Do not let -Bz trigger x-y basemap (#4290)

* Do not let -Bz trigger x-y basemap

Closes #4181.

* Update gmt_init.c

Author: PaulWessel

src/gmt_init.c

@@ -3624,8 +3624,10 @@ GMT_LOCAL int gmtinit_set_titem (struct GMT_CTRL *GMT, struct GMT_PLOT_AXIS *A,
 			break;
 	}
 
-	GMT->current.map.frame.draw = true;
-	if (axis == 'z') GMT->current.map.frame.drawz = true;
+	if (axis == 'z')
+		GMT->current.map.frame.drawz = true;
+	else
+		GMT->current.map.frame.draw = true;
 
 	return (GMT_NOERROR);
 }
@@ -3656,8 +3658,10 @@ GMT_LOCAL int gmtinit_decode_tinfo (struct GMT_CTRL *GMT, int axis, char flag, c
 			if (n_int[1]) A->item[GMT_ANNOT_UPPER+!GMT->current.map.frame.primary].special = true;	/* custom interval annotations */
 			if (n_int[2]) A->item[GMT_TICK_UPPER+!GMT->current.map.frame.primary].special = true;	/* custom tick annotations */
 			if (n_int[3]) A->item[GMT_GRID_UPPER+!GMT->current.map.frame.primary].special = true;	/* custom gridline annotations */
-			GMT->current.map.frame.draw = true;
-			if (axis == GMT_Z) GMT->current.map.frame.drawz = true;
+			if (axis == GMT_Z)
+				GMT->current.map.frame.drawz = true;
+			else
+				GMT->current.map.frame.draw = true;
 		}
 		else
 			GMT_Report (GMT->parent, GMT_MSG_ERROR, "Cannot access custom file in -B string %c-component %s\n", str[axis], &in[1]);
@@ -3785,8 +3789,10 @@ GMT_LOCAL int gmtinit_parse4_B_option (struct GMT_CTRL *GMT, char *in) {
 
 		if (!info[i][0]) continue;	 /* Skip empty format string */
 		if (info[i][0] == '0' && !info[i][1]) {	 /* Skip format '0' */
-			GMT->current.map.frame.draw = true;
-			if (i == GMT_Z) GMT->current.map.frame.drawz = true;
+			if (i == GMT_Z)
+				GMT->current.map.frame.drawz = true;
+			else
+				GMT->current.map.frame.draw = true;
 			continue;
 		}