do not persist browse tabs across sessions

gui/griffon-app/models/com/muwire/gui/MainFrameModel.groovy

@@ -85,6 +85,7 @@ class MainFrameModel {
     @Observable boolean routerPresent
 
     def results = new ConcurrentHashMap<>()
+    def browses = new ConcurrentHashSet<String>()
     def downloads = []
     def uploads = []
     boolean treeVisible = true

gui/griffon-app/views/com/muwire/gui/BrowseView.groovy

@@ -186,6 +186,7 @@ class BrowseView {
         controller.register()
         
         def mainFrameGroup = application.mvcGroupManager.findGroup("MainFrame")
+        mainFrameGroup.model.browses.add(model.host.getHumanReadableName())
         parent = mainFrameGroup.view.builder.getVariable("result-tabs")
         parent.addTab(model.host.getHumanReadableName(), p)
         
@@ -225,6 +226,9 @@ class BrowseView {
     }
     
     def closeTab = {
+        def mainFrameGroup = application.mvcGroupManager.findGroup("MainFrame")
+        mainFrameGroup.model.browses.remove(model.host.getHumanReadableName())
+        
         int index = parent.indexOfTab(model.host.getHumanReadableName())
         parent.removeTabAt(index)
         model.downloadActionEnabled = false

gui/griffon-app/views/com/muwire/gui/MainFrameView.groovy

@@ -1525,6 +1525,7 @@ class MainFrameView {
         int count = tabbedPane.getTabCount()
         for (int i = 0; i < count; i++)
             settings.openTabs.add(tabbedPane.getTitleAt(i))
+        settings.openTabs.removeAll(model.browses)
         
             
         JFrame mainFrame = builder.getVariable("main-frame")