Fix build

app/src/main/java/com/fongmi/android/tv/utils/Util.java

@@ -112,7 +112,7 @@ public class Util {
             StringBuilder sb = new StringBuilder();
             NetworkInterface nif = NetworkInterface.getByName(name);
             for (byte b : nif.getHardwareAddress()) sb.append(String.format("%02X:", b));
-            return sb.substring(0, sb.length() - 1);
+            return substring(sb.toString());
         } catch (Exception e) {
             return "";
         }
@@ -124,6 +124,15 @@ public class Util {
         return model.startsWith(manufacturer) ? model : manufacturer + " " + model;
     }
 
+    public static String substring(String text) {
+        return substring(text, 1);
+    }
+
+    public static String substring(String text, int num) {
+        if (text != null && text.length() > num) return text.substring(0, text.length() - num);
+        return text;
+    }
+
     public static long format(SimpleDateFormat format, String src) {
         try {
             return format.parse(src).getTime();