Do concealing in syntax file only if enabled.

[kristijanhusak]

I installed indentLine plugin, and got issues like mentioned in issue #23.

Since setting

let g:vim_json_syntax_conceal = 0 and
let g:indentLine_noConcealCursor="" or let g:indentLine_noConcealCursor="nc"

didn't work out properly, i noticed that when conceal is disabled manually (set to 0), syntax file still does concealing. Only the conceal cursor and level are not handled in that case. IndentLine sets conceallevel to 2, which automatically enables it for json, and i believe when someone disables the concealing manually expects not to have any of those functionality enabled, even when concealcursor/conceallevel is changed.

This is fixing the problem. I'm just not sure if it's good practice to use variables in syntax files.

[elzr]

Thanks for noticing & fixing this edge case @kristijanhusak! I liked your solution and it seems acceptable practice to me :)

[kristijanhusak]

;) Great! Thanks for merging! :)