[LyX/master] Fix wrong test: boolean variable is never negative

[Jean-Marc Lasgouttes]

commit c559f85ccb3040af4117daa139a7a2c9c1f12b8a
Author: Jean-Marc Lasgouttes <lasgout...@lyx.org>
Date:   Sat Nov 1 16:02:34 2014 +0100

    Fix wrong test: boolean variable is never negative
    
    This has been spotted by clang++.

diff --git a/src/Server.cpp b/src/Server.cpp
index 1de758a..b7fa35e 100644
--- a/src/Server.cpp
+++ b/src/Server.cpp
@@ -878,7 +878,7 @@ void LyXComm::endPipe(int & fd, string const & filename, 
bool write)
                       << '\n' << strerror(errno) << endl;
        }
 
-       if (FileName(filename).removeFile() < 0) {
+       if (!FileName(filename).removeFile()) {
                lyxerr << "LyXComm: Could not remove pipe " << filename
                       << '\n' << strerror(errno) << endl;
        }