assert absolute value for toner indicator

lib/pages/printer_details/toner_indicator.dart

@@ -28,7 +28,7 @@ class TonerIndicator extends StatelessWidget {
           Align(
             alignment: Alignment.centerLeft,
             child: Container(
-              width: (value ?? 0) / 100 * width,
+              width: ((value ?? 0) / 100 * width).abs(),
               color: color,
             ),
           ),