[libgtop/benoit/gnome-2-36] Add NULL pointer checker (bug found with scan-build).

[Benoît Dejean <bdejean src gnome org>]

commit e0f97e7dbd6ec87103705d3e114876d44cb0ca4c
Author: Benoît Dejean <bdejean gmail com>
Date:   Mon May 1 06:31:54 2017 +0200

    Add NULL pointer checker (bug found with scan-build).

 sysdeps/common/error.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/sysdeps/common/error.c b/sysdeps/common/error.c
index 0502271..6ca947b 100644
--- a/sysdeps/common/error.c
+++ b/sysdeps/common/error.c
@@ -46,7 +46,7 @@ print_message (const glibtop *server, int message_level, const char *format, int
 
        g_string_printf(message, "%s", (server && server->name ? server->name : DEFAULT_NAME));
 
-       if (server->pid) {
+       if (server && server->pid) {
                g_string_append_printf(message, "(c=%u/s=%u)", getpid(), server->pid);
        }
        else {