Separate Neopixel followup (#19287)

Marlin/src/inc/SanityCheck.h

 #if ENABLED(NEOPIXEL_LED)
   #if !PIN_EXISTS(NEOPIXEL) || NEOPIXEL_PIXELS == 0
     #error "NEOPIXEL_LED requires NEOPIXEL_PIN and NEOPIXEL_PIXELS."
-  #elif ENABLED(NEOPIXEL2_SEPARATE) && !(NEOPIXEL2_TYPE && PIN_EXISTS(NEOPIXEL2) && NEOPIXEL2_PIXELS > 0)
-    #error "NEOPIXEL2_SEPARATE requires NEOPIXEL2_PIN, NEOPIXEL2_TYPE and NEOPIXEL2_PIXELS."
+  #elif ENABLED(NEOPIXEL2_SEPARATE) && !(defined(NEOPIXEL2_TYPE) && PIN_EXISTS(NEOPIXEL2) && NEOPIXEL2_PIXELS > 0)
+    #error "NEOPIXEL2_SEPARATE requires NEOPIXEL2_TYPE, NEOPIXEL2_PIN and NEOPIXEL2_PIXELS."
   #elif ENABLED(NEO2_COLOR_PRESETS) && DISABLED(NEOPIXEL2_SEPARATE)
     #error "NEO2_COLOR_PRESETS requires NEOPIXEL2_SEPARATE to be enabled."
   #endif