[LyX/master] fix compilation when libmagic is not used

[Jean-Marc Lasgouttes]

commit c9fd7058abb4210f1640cdda7ecd86ba0473184c
Author: Jean-Marc Lasgouttes <lasgout...@lyx.org>
Date:   Tue Jul 3 21:18:26 2018 +0200

    fix compilation when libmagic is not used
---
 src/support/Magic.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/src/support/Magic.h b/src/support/Magic.h
index ca87f0c..69ea3a6 100644
--- a/src/support/Magic.h
+++ b/src/support/Magic.h
@@ -67,7 +67,7 @@ public:
                LYXERR(Debug::GRAPHICS, "Magic: libmagic support not 
configured");
        }
 
-       std::string file(std::string const & name) const { return empty_string; 
}
+       std::string file(std::string const & ) const { return empty_string(); }
 };
 
 #endif // HAVE_MAGIC_T