[smuxi/stable] Frontend-GNOME: handle empty TreeView/Store in ChatTreeView gracefully

[Mirco M. M. Bauer <mmmbauer src gnome org>]

commit 0f9cb3f504d542e7b3d734efe99546d7635ab966
Author: Mirco Bauer <meebey meebey net>
Date:   Sun Jun 11 14:43:10 2017 +0800

    Frontend-GNOME: handle empty TreeView/Store in ChatTreeView gracefully
    
    ChatTreeView.set_CurrentChatView() and GetPath(rowNumber) are ignoring the
    result of TreeStore.GetIterFirst() which might fail and thus iter remains
    Gtk.TreeIter.Zero which then would trigger Gtk-CRITICAL messages for the
    following method calls on that Zero iter.

 src/Frontend-GNOME/Views/ChatTreeView.cs |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)
---
diff --git a/src/Frontend-GNOME/Views/ChatTreeView.cs b/src/Frontend-GNOME/Views/ChatTreeView.cs
index e51b4d3..2e87e37 100644
--- a/src/Frontend-GNOME/Views/ChatTreeView.cs
+++ b/src/Frontend-GNOME/Views/ChatTreeView.cs
@@ -43,7 +43,10 @@ namespace Smuxi.Frontend.Gnome
             set {
                 Gtk.TreeIter iter;
                 if (value == null) {
-                    TreeStore.GetIterFirst(out iter);
+                    if (!TreeStore.GetIterFirst(out iter)) {
+                        // no chat views available; this can happen on shutdown
+                        return;
+                    }
                 } else {
                     iter = FindChatIter(value);
                     if (Gtk.TreeIter.Zero.Equals(iter)) {
@@ -508,7 +511,9 @@ namespace Smuxi.Frontend.Gnome
         Gtk.TreePath GetPath(int rowNumber)
         {
             Gtk.TreeIter iter;
-            TreeStore.GetIterFirst(out iter);
+            if (!TreeStore.GetIterFirst(out iter)) {
+                return null;
+            }
             var path = TreeStore.GetPath(iter);
             // TODO: clamp upper limit
             int i;