[balsa] Reset adjustments only when displaying a real part

[Peter Bloomfield <peterb src gnome org>]

commit 78811da6eea9c2db7d31ab84fd5618751b138792
Author: Peter Bloomfield <PeterBloomfield bellsouth net>
Date:   Fri Apr 7 20:11:43 2017 -0400

    Reset adjustments only when displaying a real part
    
        * src/balsa-message.c (select_part): reset adjustments only when
          displaying a real message part.

 ChangeLog           |    5 +++++
 src/balsa-message.c |   13 ++++++++-----
 2 files changed, 13 insertions(+), 5 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 5a311de..64b42e3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2017-04-07  Peter Bloomfield  <pbloomfield bellsouth net>
+
+       * src/balsa-message.c (select_part): reset adjustments only when
+         displaying a real message part.
+
 2017-04-07  Albrecht Dreß
 
 Do not emit a critical warning
diff --git a/src/balsa-message.c b/src/balsa-message.c
index 2661807..292c088 100644
--- a/src/balsa-message.c
+++ b/src/balsa-message.c
@@ -2283,7 +2283,6 @@ static void
 select_part(BalsaMessage * bm, BalsaPartInfo *info)
 {
     LibBalsaMessageBody *body;
-    GtkAdjustment *hadj, *vadj;
 
     hide_all_parts(bm);
     bm_disable_find_entry(bm);
@@ -2293,10 +2292,14 @@ select_part(BalsaMessage * bm, BalsaPartInfo *info)
 
     g_signal_emit(G_OBJECT(bm), balsa_message_signals[SELECT_PART], 0);
 
-    g_object_get(G_OBJECT(bm->scroll), "hadjustment", &hadj,
-                                              "vadjustment", &vadj, NULL);
-    gtk_adjustment_set_value(hadj, 0);
-    gtk_adjustment_set_value(vadj, 0);
+    if (body != NULL) {
+        GtkAdjustment *hadj, *vadj;
+
+        g_object_get(G_OBJECT(bm->scroll), "hadjustment", &hadj,
+                                           "vadjustment", &vadj, NULL);
+        gtk_adjustment_set_value(hadj, 0);
+        gtk_adjustment_set_value(vadj, 0);
+    }
 }
 
 GtkWidget *