War on -Werror, part 12: explicit bool usage.

It may save a few cycles, but it's best to be
explicit on boolean operations, especially with
ASSERT.

src/NotesLoaderBMS.cpp

@@ -1268,7 +1268,7 @@ bool BMSLoader::LoadFromDir( const RString &sDir, Song &out )
 
 	/* We should have at least one; if we had none, we shouldn't have been
 	 * called to begin with. */
-	ASSERT( arrayBMSFileNames.size() );
+	ASSERT( arrayBMSFileNames.size() != 0 );
 
 	BMSSongLoader loader( sDir, &out );
 	for( unsigned i=0; i<arrayBMSFileNames.size(); i++ )