Higher textview in Invite Friends! widow. See #2095.

data/glade/chat_to_muc_window.glade

@@ -34,6 +34,7 @@ Select the contacts you want to invite</property>
             <property name="shadow_type">GTK_SHADOW_IN</property>
             <child>
               <widget class="GtkTreeView" id="guests_treeview">
+                <property name="height_request">300</property>
                 <property name="visible">True</property>
                 <property name="can_focus">True</property>
                 <property name="headers_visible">False</property>