Fixed a Null Pointer Exception when Wifi Settings is indexing.

                // set the icon (drawable) to that state's drawable.

                StateListDrawable sld = (StateListDrawable) context.getTheme()

                        .obtainStyledAttributes(wifi_signal_attributes).getDrawable(0);

                // If sld is null then we are indexing and therefore do not have access to

                // (nor need to display) the drawable.

                if (sld != null) {

                    sld.setState((security != SECURITY_NONE) ? STATE_SECURED : STATE_NONE);

                    drawable = sld.getCurrent();

                    setIcon(drawable);

                }

            }

            if (drawable != null) {

                drawable.setLevel(level);