Heater error status

Marlin/src/lcd/HD44780/marlinui_HD44780.cpp

@@ -535,7 +535,7 @@ FORCE_INLINE void _draw_heater_status(const heater_id_t heater_id, const char pr
 
   if (prefix >= 0) lcd_put_wchar(prefix);
 
-  lcd_put_u8str(i16tostr3rj(t1));
+  lcd_put_u8str(t1 < 0 ? "err" : i16tostr3rj(t1));
   lcd_put_wchar('/');
 
   #if !HEATER_IDLE_HANDLER

Marlin/src/lcd/dogm/status_screen_DOGM.cpp

@@ -186,10 +186,14 @@
 #define PROGRESS_BAR_WIDTH (LCD_PIXEL_WIDTH - PROGRESS_BAR_X)
 
 FORCE_INLINE void _draw_centered_temp(const celsius_t temp, const uint8_t tx, const uint8_t ty) {
-  const char *str = i16tostr3rj(temp);
-  const uint8_t len = str[0] != ' ' ? 3 : str[1] != ' ' ? 2 : 1;
-  lcd_put_u8str(tx - len * (INFO_FONT_WIDTH) / 2 + 1, ty, &str[3-len]);
-  lcd_put_wchar(LCD_STR_DEGREE[0]);
+  if (temp < 0)
+    lcd_put_u8str(tx - 3 * (INFO_FONT_WIDTH) / 2 + 1, ty, "err");
+  else {
+    const char *str = i16tostr3rj(temp);
+    const uint8_t len = str[0] != ' ' ? 3 : str[1] != ' ' ? 2 : 1;
+    lcd_put_u8str(tx - len * (INFO_FONT_WIDTH) / 2 + 1, ty, &str[3-len]);
+    lcd_put_wchar(LCD_STR_DEGREE[0]);
+  }
 }
 
 #if DO_DRAW_FLOWMETER