Allow boards without a thermistor

Marlin/SanityCheck.h

@@ -770,7 +770,7 @@ static_assert(1 >= 0
  */
 #if !HAS_HEATER_0
   #error "HEATER_0_PIN not defined for this board."
-#elif !PIN_EXISTS(TEMP_0)
+#elif !PIN_EXISTS(TEMP_0) && !(defined(MAX6675_SS) && MAX6675_SS >= 0)
   #error "TEMP_0_PIN not defined for this board."
 #elif !PIN_EXISTS(E0_STEP) || !PIN_EXISTS(E0_DIR) || !PIN_EXISTS(E0_ENABLE)
   #error "E0_STEP_PIN, E0_DIR_PIN, or E0_ENABLE_PIN not defined for this board."

Marlin/ultralcd.cpp

@@ -1564,9 +1564,9 @@ void kill_screen(const char* lcd_msg) {
      */
     void _lcd_level_bed_homing() {
       if (lcdDrawUpdate) lcd_implementation_drawedit(PSTR(MSG_LEVEL_BED_HOMING), NULL);
-      lcdDrawUpdate = LCDVIEW_KEEP_REDRAWING;
       if (axis_homed[X_AXIS] && axis_homed[Y_AXIS] && axis_homed[Z_AXIS])
         lcd_goto_screen(_lcd_level_bed_homing_done);
+      lcdDrawUpdate = LCDVIEW_KEEP_REDRAWING;
     }
 
     /**