Wi-Fi grey out fix on iPhone4S

Possible solution to "Wi-Fi button greyed out"

on iPhone4S running IOS 7.1.2

I tried the following and it is working for me:

1 - Go to settings and find Wallpaper and Brightness

2 - Set your Wallpaper to all Black [no imagery]

3 - Set your Brightness to below 50%

4- Turn phone off and back on