How to get rid of "SD Card blank or has unsupported filesystem" notification
SD Card blank or has unsupported filesystem means your SD Card has corrupted data.

The only way is to get it normal is to Format it. 

Now what about the Data on SD Card ?
If you are using Linux Machine then there is something called TestDisk. Install it on your PC. Now connect your phone with SD Card inserted to you PC. Run TestDisk and follow the options that it shows. Backup the Uncorrupted Data to your PC and format the SD Card from your Phone.