[Cppcms-users] Blank value within csrf field

[tuq3 <tu...@ya...>]

Hi everyone!
First of I put <%= csrf =%> into <from></form> and while loading page 
with this form i get error:
cppcms, error: Caught exception [Session storage backend is not loaded].
I managed it by adding "session" preferences into config.js, but now I 
get a blank value within csrf hidden field after loading a page.