[balsa] Assert that getpwuid returns a valid structure

[Peter Bloomfield <peterb src gnome org>]

commit 2132973b6a5ebb3bf27fa12385b723544d8b908f
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Mon Jun 26 18:35:20 2017 -0400

    Assert that getpwuid returns a valid structure
    
        * libbalsa/rfc3156.c (gpg_updates_trustdb): Assert that
          getpwuid returns a valid passwd structure.

 libbalsa/rfc3156.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)
---
diff --git a/libbalsa/rfc3156.c b/libbalsa/rfc3156.c
index 59527dc..fe94f8e 100644
--- a/libbalsa/rfc3156.c
+++ b/libbalsa/rfc3156.c
@@ -1035,12 +1035,17 @@ gpg_updates_trustdb(void)
     struct passwd *pwent;
     struct stat stat_buf;
 
-    if (!lockname)
-       if ((pwent = getpwuid(getuid())))
+    if (lockname == NULL) {
+       if ((pwent = getpwuid(getuid())) != NULL) {
            lockname =
                g_strdup_printf("%s/.gnupg/trustdb.gpg.lock",
                                pwent->pw_dir);
-    if (!stat(lockname, &stat_buf)) {
+        } else {
+            g_assert_not_reached();
+        }
+    }
+
+    if (stat(lockname, &stat_buf) == 0) {
        libbalsa_information(LIBBALSA_INFORMATION_ERROR, "%s%s",
                             _
                             ("GnuPG is rebuilding the trust database and is currently unavailable."),