[evolution] Avoid NULL dereference in mail-send-recv.c:free_send_data() function

[Milan Crha <mcrha src gnome org>]

commit 362d39a5e15a331f5659084ecfa6c4557018f2fc
Author: Milan Crha <mcrha redhat com>
Date:   Mon May 23 13:26:06 2016 +0200

    Avoid NULL dereference in mail-send-recv.c:free_send_data() function
    
    This had been reported downstream as:
    https://bugzilla.redhat.com/show_bug.cgi?id=1338561

 mail/mail-send-recv.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/mail/mail-send-recv.c b/mail/mail-send-recv.c
index 279a63b..08b0d1e 100644
--- a/mail/mail-send-recv.c
+++ b/mail/mail-send-recv.c
@@ -200,6 +200,9 @@ free_send_data (void)
 {
        struct _send_data *data = send_data;
 
+       if (!data)
+               return;
+
        g_return_if_fail (g_hash_table_size (data->active) == 0);
 
        if (data->inbox) {