Fix misleading if-statement
Fix misleading if-statement

GCC 6 introduced -Wmisleading-warnings. It reveals this misleading
if-statement. "@" should not really be added if username is not
specified, however I am convinced that this function is never called
without username...

gicmo/gvfs,gicmo/gvfs,gicmo/gvfs,gicmo/gvfs