Fix planner.cpp compile (#16996)

Marlin/src/module/planner.cpp

@@ -2403,10 +2403,10 @@ bool Planner::_populate_block(block_t * const block, bool split_move,
       LOOP_XYZE(i)
     #endif
     {
-      const float jerk = ABS(current_speed[i]);   // cs : Starting from zero, change in speed for this axis
-                  maxj = (max_jerk[axis]          // mj : The max jerk setting for this axis
+      const float jerk = ABS(current_speed[i]),   // cs : Starting from zero, change in speed for this axis
+                  maxj = (max_jerk[i]             // mj : The max jerk setting for this axis
                     #ifdef TRAVEL_EXTRA_XYJERK
-                      + (axis == X_AXIS || axis == Y_AXIS ? extra_xyjerk : 0)
+                      + (i == X_AXIS || i == Y_AXIS ? extra_xyjerk : 0)
                     #endif
                   );