[gom] gom: Store NULL GDateTimes in the database as NULL

[Bastien Nocera <hadess src gnome org>]

commit e80ff4910c8a481fbb0616cd0ef16d6329132da6
Author: Bob Ham <bob ham puri sm>
Date:   Wed Jul 17 14:44:15 2019 +0100

    gom: Store NULL GDateTimes in the database as NULL
    
    Currently Gom will store NULL GDateTimes in the database as a string
    representing the epoch, '1970-01-01T00:00:00Z', instead of NULL.  This
    unneccessarily increases the storage requirements of every NULL
    GDateTime column in every row by 20 bytes.  This also presents a loss
    of information: there's no way to distinguish between the valid input
    values of the epoch and NULL.  The API user has to account for the way
    in which the library is transforming data values.
    
    To fix this, we store NULL GDateTime values in the database as NULL
    instead.

 gom/gom-command.c | 6 +++---
 gom/gom-cursor.c  | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)
---
diff --git a/gom/gom-command.c b/gom/gom-command.c
index a66050c..abad299 100644
--- a/gom/gom-command.c
+++ b/gom/gom-command.c
@@ -106,13 +106,13 @@ gom_command_bind_param (GomCommand   *command,
       break;
    default:
       if (G_VALUE_TYPE(value) == G_TYPE_DATE_TIME) {
-         GTimeVal tv = { 0 };
          GDateTime *dt = g_value_get_boxed(value);
-         gchar *iso8601;
+         gchar *iso8601 = NULL;
          if (dt) {
+            GTimeVal tv = { 0 };
             g_date_time_to_timeval(dt, &tv);
+            iso8601 = g_time_val_to_iso8601(&tv);
          }
-         iso8601 = g_time_val_to_iso8601(&tv);
          sqlite3_bind_text(priv->stmt, param, iso8601, -1, g_free);
          break;
       } else if (G_VALUE_TYPE(value) == G_TYPE_STRV) {
diff --git a/gom/gom-cursor.c b/gom/gom-cursor.c
index 6d21ae4..6ffdc28 100644
--- a/gom/gom-cursor.c
+++ b/gom/gom-cursor.c
@@ -86,13 +86,13 @@ gom_cursor_get_column (GomCursor *cursor,
       break;
    default:
       if (G_VALUE_TYPE(value) == G_TYPE_DATE_TIME) {
-         GTimeVal tv = { 0 };
-         GDateTime *dt;
          const gchar *iso8601 = (gchar *)sqlite3_column_text(priv->stmt, column);
+         GDateTime *dt = NULL;
          if (iso8601) {
+            GTimeVal tv = { 0 };
             g_time_val_from_iso8601(iso8601, &tv);
+            dt = g_date_time_new_from_timeval_utc(&tv);
          }
-         dt = g_date_time_new_from_timeval_utc(&tv);
          g_value_take_boxed(value, dt);
          break;
       }