prevent warning when compiling in release mode
prevent warning when compiling in release mode

In release mode asserts are ignored, so variables which are only
used in asserts give off unused warnings. This one was particularily
noisy.

Change-Id: I4236449f76cdffaac5f8c44f745139f5b8dfa64b
Tuleap: #211

savoirfairelinux/ring-lrc,savoirfairelinux/ring-lrc,savoirfairelinux/ring-lrc,savoirfairelinux/ring-lrc,savoirfairelinux/ring-lrc