[vte] app: Add sanity checks

[Christian Persch <chpe src gnome org>]

commit f85d4fcf75539bbf34d40f90f877e90206d41a1e
Author: Christian Persch <chpe gnome org>
Date:   Thu Dec 10 18:42:18 2015 +0100

    app: Add sanity checks

 src/app.vala |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/src/app.vala b/src/app.vala
index 516623a..cb0a4ce 100644
--- a/src/app.vala
+++ b/src/app.vala
@@ -778,13 +778,16 @@ class App : Gtk.Application
   {
     base.startup();
 
-    for (uint i = 0; i < App.Options.n_windows; i++)
+    for (uint i = 0; i < App.Options.n_windows.clamp(0, 16); i++)
       new Window(this);
   }
 
   protected override void activate()
   {
     foreach (Gtk.Window win in this.get_windows()) {
+      if (!(win is Window))
+        continue;
+
       var window = win as Window;
       window.apply_geometry();
       window.present();