[libgda] browser: fix segfault on data source init

[Daniel Espinosa Ortiz <despinosa src gnome org>]

commit ce406110de481fb3e2e664f539173978e66d8758
Author: Daniel Espinosa Ortiz <esodan gmail com>
Date:   Sun Feb 17 18:34:10 2019 -0600

    browser: fix segfault on data source init

 tools/browser/data-manager/data-source-editor.c | 43 ++++++++++++++++---------
 1 file changed, 27 insertions(+), 16 deletions(-)
---
diff --git a/tools/browser/data-manager/data-source-editor.c b/tools/browser/data-manager/data-source-editor.c
index 9a677830b..9a50f1347 100644
--- a/tools/browser/data-manager/data-source-editor.c
+++ b/tools/browser/data-manager/data-source-editor.c
@@ -155,32 +155,43 @@ data_source_editor_init (DataSourceEditor *editor)
 
        GdaHolder *holder;
        holder = gda_set_get_holder (editor->priv->attributes, "id");
-       g_object_set ((GObject*) holder, "name", _("Id"),
+       if (holder) {
+               g_object_set ((GObject*) holder, "name", _("Id"),
                      "description",
-                     _("Data source's ID\n"
-                       "(as referenced by other data sources)"), NULL);
-       gdaui_basic_form_entry_set_editable (GDAUI_BASIC_FORM (form), holder, FALSE);
+                     _("Data source's ID\n(as referenced by other data sources)"), NULL);
+               gdaui_basic_form_entry_set_editable (GDAUI_BASIC_FORM (form), holder, FALSE);
+       }
 
        holder = gda_set_get_holder (editor->priv->attributes, "descr");
-       g_object_set ((GObject*) holder, "name", _("Description"),
+       if (holder != NULL) {
+               g_object_set ((GObject*) holder, "name", _("Description"),
                      "description", _("Data source's description"), NULL);
+       }
 
        holder = gda_set_get_holder (editor->priv->attributes, "table");
-       g_object_set ((GObject*) holder, "name", _("Table"),
-                     "description", _("Table to display data from, leave empty\n"
-                                      "to specify a SELECT statement instead"), NULL);
+
+       if (holder != NULL) {
+               g_object_set ((GObject*) holder, "name", _("Table"),
+                     "description", _("Table to display data from, leave empty\nto specify a SELECT 
statement instead"),
+                     NULL);
+       }
 
        holder = gda_set_get_holder (editor->priv->attributes, "sql");
-       g_object_set ((GObject*) holder, "name", _("SELECT\nSQL"),
-                     "description", _("Actual SQL executed\nto select data\n"
-                                      "Can't be changed if a table name is set"), NULL);
-       g_object_set ((GObject*) holder, "plugin", "text:PROG_LANG=gda-sql", NULL);
+       if (holder != NULL) {
+               g_object_set ((GObject*) holder, "name", _("SELECT\nSQL"),
+                     "description", _("Actual SQL executed\nto select data\nCan't be changed if a table name 
is set"),
+                      "plugin", "text:PROG_LANG=gda-sql",
+                      NULL);
+       }
+
 
        holder = gda_set_get_holder (editor->priv->attributes, "depend");
-       g_object_set ((GObject*) holder, "name", _("Dependencies"),
-                     "description", _("Required and provided named parameters"), NULL);
-       gdaui_basic_form_entry_set_editable (GDAUI_BASIC_FORM (form), holder, FALSE);
-       g_object_set ((GObject*) holder, "plugin", "rtext", NULL);
+       if (holder != NULL) {
+               g_object_set ((GObject*) holder, "name", _("Dependencies"),
+                     "description", _("Required and provided named parameters"),
+                     "plugin", "rtext", NULL);
+               gdaui_basic_form_entry_set_editable (GDAUI_BASIC_FORM (form), holder, FALSE);
+       }
 }
 
 static void