Fix FILAMENT_LCD_DISPLAY for disabled state

Marlin/src/lcd/ultralcd_impl_DOGM.h

     strcpy(xstring, ftostr4sign(LOGICAL_X_POSITION(current_position[X_AXIS])));
     strcpy(ystring, ftostr4sign(LOGICAL_Y_POSITION(current_position[Y_AXIS])));
     strcpy(zstring, ftostr52sp(FIXFLOAT(LOGICAL_Z_POSITION(current_position[Z_AXIS]))));
-    #if ENABLED(FILAMENT_LCD_DISPLAY) && DISABLED(SDSUPPORT)
+    #if ENABLED(FILAMENT_LCD_DISPLAY)
       strcpy(wstring, ftostr12ns(filament_width_meas));
-      strcpy(mstring, itostr3(100.0 * planner.volumetric_multiplier[FILAMENT_SENSOR_EXTRUDER_NUM]));
+      if (parser.volumetric_enabled)
+        strcpy(mstring, itostr3(100.0 * filament_width_meas / filament_width_nominal));
+      else
+        strcpy_P(mstring, PSTR("---"));
+      // Alternatively, show the ratio between cross-sectional areas:
+      //strcpy(mstring, itostr3(100.0 / CIRCLE_AREA(filament_width_nominal * 0.5)
+      //                              / planner.volumetric_multiplier[FILAMENT_SENSOR_EXTRUDER_NUM]));
     #endif
   }
 
     //
     // Filament sensor display if SD is disabled
     //
-    #if DISABLED(SDSUPPORT) && ENABLED(FILAMENT_LCD_DISPLAY)
+    #if ENABLED(FILAMENT_LCD_DISPLAY) && DISABLED(SDSUPPORT)
       u8g.setPrintPos(56, 50);
       lcd_print(wstring);
       u8g.setPrintPos(102, 50);
       else {
         lcd_printPGM(PSTR(LCD_STR_FILAM_DIA));
         u8g.print(':');
-        lcd_print(ftostr12ns(filament_width_meas));
+        lcd_print(wstring);
         lcd_printPGM(PSTR("  " LCD_STR_FILAM_MUL));
         u8g.print(':');
-        lcd_print(itostr3(100.0 * planner.volumetric_multiplier[FILAMENT_SENSOR_EXTRUDER_NUM]));
+        lcd_print(mstring);
         u8g.print('%');
       }
     #else

Marlin/src/lcd/ultralcd_impl_HD44780.h

       lcd_printPGM(PSTR("Dia "));
       lcd.print(ftostr12ns(filament_width_meas));
       lcd_printPGM(PSTR(" V"));
-      lcd.print(itostr3(100.0 * planner.volumetric_multiplier[FILAMENT_SENSOR_EXTRUDER_NUM]));
-      lcd.write('%');
+      if (parser.volumetric_enabled) {
+        lcd.print(itostr3(100.0 * filament_width_meas / filament_width_nominal));
+        lcd.write('%');
+      }
+      else
+        lcd_printPGM(PSTR("--- "));
       return;
     }
 

Marlin/src/module/temperature.cpp

   // Convert raw Filament Width to millimeters
   float Temperature::analog2widthFil() {
     return current_raw_filwidth * 5.0 * (1.0 / 16383.0);
-    //return current_raw_filwidth;
   }
 
   // Convert raw Filament Width to a ratio
   int Temperature::widthFil_to_size_ratio() {
     float temp = filament_width_meas;
-    if (temp < MEASURED_LOWER_LIMIT) temp = filament_width_nominal;  //assume sensor cut out
+    if (temp < MEASURED_LOWER_LIMIT) temp = filament_width_nominal;  // Assume a bad sensor reading
     else NOMORE(temp, MEASURED_UPPER_LIMIT);
     return filament_width_nominal / temp * 100;
   }