title: Null pointer exception in getView() of custom Adapter
body: <p>I am using this Custom Adapter for my ListView:</p>
  
  <pre><code>public class SideMenuAdapter extends BaseAdapter {
  
      private static final int TYPE_MAX_COUNT = 2;
      private static LayoutInflater inflater = null;
      private Activity activity;
      public static String[] values;
      ListView myList;
  
      public SideMenuAdapter(Activity a, String[] sa, ListView lv) {
  
          values = sa;
          activity = a;
          inflater = (LayoutInflater) activity
                  .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
          myList = lv;
      }
  
      public int getCount() {
  
          return values.length;
      }
  
      public Object getItem(int position) {
  
          return position;
      }
  
      public long getItemId(int position) {
  
          return position;
      }
  
      public static class ViewHolder {
  
          public TextView mainText;
          public TextView sideText;
      }
  
      public View getView(int position, View convertView, ViewGroup parent) {
  
          ViewHolder holder = new ViewHolder();
          View vi = convertView;
          if (vi == null) {
  
              //here i am getting NullPointerException
              vi.setTag(holder);
          } else {
  
              holder = (ViewHolder) vi.getTag();
          }
          vi = inflater.inflate(R.layout.side_menu_list_item, null);
          holder.mainText = (TextView) vi.findViewById(R.id.mainText_sideMenu);
          holder.sideText = (TextView) vi.findViewById(R.id.sideText_sideMenu);
          holder.mainText.setText(values[position]);
          if(position == 2){
  
              holder.sideText.setText("3");
              holder.sideText.setBackgroundResource(R.drawable.orange);
          }
          return convertView;
      }
      @Override
      public int getViewTypeCount() {
  
          return TYPE_MAX_COUNT;
      }
  }
  </code></pre>
  
  <p>i am setting adapter to my listview this way:</p>
  
  <pre><code>    String menuItems[] = new String[] { "My Wants", "Profile", "Notifications",
              "Feedback", "Logout" };
      listView1.setAdapter(new SideMenuAdapter(this, menuItems, listView1));
  </code></pre>
  
  <p>where am i wrong??</p>