Ensure XY known for Z safe homing

Addressing #18143

Marlin/src/gcode/calibrate/G28.cpp

 
   #else // NOT DELTA
 
-    const bool homeX = parser.seen('X'), homeY = parser.seen('Y'), homeZ = parser.seen('Z'),
+    const bool homeZ = parser.seen('Z'),
+               needX = homeZ && TERN0(Z_SAFE_HOMING, axes_need_homing(_BV(X_AXIS))),
+               needY = homeZ && TERN0(Z_SAFE_HOMING, axes_need_homing(_BV(Y_AXIS))),
+               homeX = needX || parser.seen('X'), homeY = needY || parser.seen('Y'),
                home_all = homeX == homeY && homeX == homeZ, // All or None
                doX = home_all || homeX, doY = home_all || homeY, doZ = home_all || homeZ;