That's not an error, that's a warning. Warnings will still allow full compilation.
I once worked on a project that compiled with 0 errors and over 3000 warnings. The compiled app still ran. (Wish I could remember what app that was... I think it was ArcEmu )
I once worked on a project that compiled with 0 errors and over 3000 warnings. The compiled app still ran. (Wish I could remember what app that was... I think it was ArcEmu )