Following is an easy method I have found from Internet.
Required
1. A Rooted MTK device
2. Root Explorer or Root Browser (download from Play Store)
3. Wifi Error Fix.rar (find the download link at the bottom)
Steps
1. Make sure you switch off the WIFI
2. On your rooted device go to the following location using a root explorer mentioned above
data/nvram/APCFG/APRDEB
3. Delete the following files from the above location
WIFI
WIFI_CUSTOM
4. Now extract the files from the WiFi fix.rar and copy / move them to the above location (data/nvram/APCFG/APRDEB)
5. Reboot the device and switch on the WIFI. That's it, it's gone.
I tested this on Lenovo a3000
Update: Broken link for download updated. Many people have requested permission. Sorry for the inconvenience.
Download
Download