Ensure Z_PROBE_PIN is defined if Z_PROBE_AND_ENDSTOP is.

Marlin/SanityCheck.h

@@ -103,8 +103,11 @@
      * Require a Z Probe Pin if Z_PROBE_AND_ENDSTOP is enabled.
      */
     #if defined(Z_PROBE_AND_ENDSTOP)
+      #ifndef Z_PROBE_PIN
+        #error You must have a Z_PROBE_PIN defined in your pins_XXXX.h file if you enable Z_PROBE_AND_ENDSTOP
+      #endif
       #if Z_PROBE_PIN == -1
-        #error You must have a Z_PROBE_PIN defined if you enable Z_PROBE_AND_ENDSTOP
+        #error You must set Z_PROBE_PIN to a valid pin if you enable Z_PROBE_AND_ENDSTOP
       #endif
       #ifndef NUM_SERVOS
         #error You must have NUM_SERVOS defined and there must be at least 1 configured to use Z_PROBE_AND_ENDSTOP