Allow TEMP_STAT_LEDS with only one LED defined

Marlin/Marlin_main.cpp

       bool new_led = (max_temp > 55.0) ? true : (max_temp < 54.0) ? false : red_led;
       if (new_led != red_led) {
         red_led = new_led;
-        WRITE(STAT_LED_RED_PIN, new_led ? HIGH : LOW);
-        WRITE(STAT_LED_BLUE_PIN, new_led ? LOW : HIGH);
+        #if PIN_EXISTS(STAT_LED_RED)
+          WRITE(STAT_LED_RED_PIN, new_led ? HIGH : LOW);
+          #if PIN_EXISTS(STAT_LED_BLUE)
+            WRITE(STAT_LED_BLUE_PIN, new_led ? LOW : HIGH);
+          #endif
+        #else
+          WRITE(STAT_LED_BLUE_PIN, new_led ? HIGH : LOW);
+        #endif
       }
     }
   }

Marlin/SanityCheck.h

 /**
  * Temperature status LEDs
  */
-#if ENABLED(TEMP_STAT_LEDS) && !(PIN_EXISTS(STAT_LED_RED) && PIN_EXISTS(STAT_LED_BLUE))
-  #error "TEMP_STAT_LEDS requires STAT_LED_RED_PIN and STAT_LED_BLUE_PIN."
+#if ENABLED(TEMP_STAT_LEDS) && !PIN_EXISTS(STAT_LED_RED) && !PIN_EXISTS(STAT_LED_BLUE)
+  #error "TEMP_STAT_LEDS requires STAT_LED_RED_PIN or STAT_LED_BLUE_PIN, preferably both."
 #endif
 
 /**
 #else
   #define COUNT_LCD_13 COUNT_LCD_12
 #endif
-#if ENABLED(REPRAPWORLD_KEYPAD)
+#if ENABLED(REPRAPWORLD_KEYPAD) && DISABLED(CARTESIO_UI)
   #define COUNT_LCD_14 INCREMENT(COUNT_LCD_13)
 #else
   #define COUNT_LCD_14 COUNT_LCD_13