Suppress redundant serial errors

Marlin/src/HAL/STM32F1/HAL.h

@@ -84,46 +84,58 @@
   #define MYSERIAL1 UsbSerial
 #elif WITHIN(SERIAL_PORT, 1, NUM_UARTS)
   #define MYSERIAL1 MSERIAL(SERIAL_PORT)
-#elif NUM_UARTS == 5
+#else
+  #define MYSERIAL1 MSERIAL(1) // dummy port
+  #if NUM_UARTS == 5
     #error "SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
   #else
     #error "SERIAL_PORT must be -1 or from 1 to 3. Please update your configuration."
   #endif
+#endif
 
 #ifdef SERIAL_PORT_2
   #if SERIAL_PORT_2 == -1
     #define MYSERIAL2 UsbSerial
   #elif WITHIN(SERIAL_PORT_2, 1, NUM_UARTS)
     #define MYSERIAL2 MSERIAL(SERIAL_PORT_2)
-  #elif NUM_UARTS == 5
+  #else
+    #define MYSERIAL2 MSERIAL(1) // dummy port
+    #if NUM_UARTS == 5
       #error "SERIAL_PORT_2 must be -1 or from 1 to 5. Please update your configuration."
     #else
       #error "SERIAL_PORT_2 must be -1 or from 1 to 3. Please update your configuration."
     #endif
   #endif
+#endif
 
 #ifdef MMU2_SERIAL_PORT
   #if MMU2_SERIAL_PORT == -1
     #define MMU2_SERIAL UsbSerial
   #elif WITHIN(MMU2_SERIAL_PORT, 1, NUM_UARTS)
     #define MMU2_SERIAL MSERIAL(MMU2_SERIAL_PORT)
-  #elif NUM_UARTS == 5
+  #else
+    #define MMU2_SERIAL MSERIAL(1) // dummy port
+    #if NUM_UARTS == 5
       #error "MMU2_SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
     #else
       #error "MMU2_SERIAL_PORT must be -1 or from 1 to 3. Please update your configuration."
     #endif
   #endif
+#endif
 
 #ifdef LCD_SERIAL_PORT
   #if LCD_SERIAL_PORT == -1
     #define LCD_SERIAL UsbSerial
   #elif WITHIN(LCD_SERIAL_PORT, 1, NUM_UARTS)
     #define LCD_SERIAL MSERIAL(LCD_SERIAL_PORT)
-  #elif NUM_UARTS == 5
+  #else
+    #define LCD_SERIAL MSERIAL(1) // dummy port
+    #if NUM_UARTS == 5
       #error "LCD_SERIAL_PORT must be -1 or from 1 to 5. Please update your configuration."
     #else
       #error "LCD_SERIAL_PORT must be -1 or from 1 to 3. Please update your configuration."
     #endif
+  #endif
   #if HAS_DGUS_LCD
     #define SERIAL_GET_TX_BUFFER_FREE() LCD_SERIAL.availableForWrite()
   #endif

Marlin/src/lcd/extui/lib/dgus/mks/DGUSScreenHandler.h

@@ -158,7 +158,6 @@ public:
     static void GetManualFilamentSpeed(DGUS_VP_Variable &var, void *val_ptr);
   #endif
 
-  
   #if ENABLED(SDSUPPORT)
     // Callback for VP "Display wants to change screen when there is a SD card"
     static void ScreenChangeHookIfSD(DGUS_VP_Variable &var, void *val_ptr);