util/error: Remove an unnecessary NULL check

This NULL check was required while introduced in 680d16dc.
Later refactor added a NULL check in error_setv(), so this check
is now redundant.
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20190302223825.11192-2-philmd@redhat.com>
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

util/error.c

@@ -103,10 +103,6 @@ void error_setg_errno_internal(Error **errp,
     va_list ap;
     int saved_errno = errno;
 
-    if (errp == NULL) {
-        return;
-    }
-
     va_start(ap, fmt);
     error_setv(errp, src, line, func, ERROR_CLASS_GENERIC_ERROR, fmt, ap,
                os_errno != 0 ? strerror(os_errno) : NULL);