Fix the plugin Disabled route as it has never been tested

Stop plugins being available if the database is more advanced than the code.

bzr-revno: 1815

openlp/core/lib/db.py

@@ -182,6 +182,7 @@ class Manager(object):
         settings.beginGroup(plugin_name)
         self.db_url = u''
         self.is_dirty = False
+        self.session = None
         db_type = unicode(
             settings.value(u'db type', QtCore.QVariant(u'sqlite')).toString())
         if db_type == u'sqlite':

openlp/core/lib/pluginmanager.py

@@ -158,6 +158,8 @@ class PluginManager(object):
         for plugin in self.plugins:
             if plugin.status is not PluginStatus.Disabled:
                 plugin.settings_tab = plugin.getSettingsTab(settings_form)
+            else:
+                plugin.settings_tab = None
         settings_form.plugins = self.plugins
 
     def hook_import_menu(self, import_menu):

openlp/core/ui/pluginform.py

@@ -117,16 +117,17 @@ class PluginForm(QtGui.QDialog, Ui_PluginViewDialog):
             self.pluginListWidget.currentItem().text().split(u'(')[0][:-1]
         self.activePlugin = None
         for plugin in self.parent().pluginManager.plugins:
-            if plugin.nameStrings[u'singular'] == plugin_name_singular:
-                self.activePlugin = plugin
-                break
+            if plugin.status != PluginStatus.Disabled:
+                if plugin.nameStrings[u'singular'] == plugin_name_singular:
+                    self.activePlugin = plugin
+                    break
         if self.activePlugin:
             self._setDetails()
         else:
             self._clearDetails()
 
     def onStatusComboBoxChanged(self, status):
-        if self.programaticChange:
+        if self.programaticChange or status == PluginStatus.Disabled:
             return
         if status == 0:
             Receiver.send_message(u'cursor_busy')

openlp/plugins/songs/songsplugin.py

@@ -64,6 +64,9 @@ class SongsPlugin(Plugin):
         self.icon_path = u':/plugins/plugin_songs.png'
         self.icon = build_icon(self.icon_path)
 
+    def checkPreConditions(self):
+        return self.manager.session is not None
+
     def initialise(self):
         log.info(u'Songs Initialising')
         Plugin.initialise(self)

openlp/plugins/songusage/songusageplugin.py

@@ -54,6 +54,9 @@ class SongUsagePlugin(Plugin):
         self.inactiveIcon = build_icon(u':/songusage/song_usage_inactive.png')
         self.songUsageActive = False
 
+    def checkPreConditions(self):
+        return self.manager.session is not None
+
     def addToolsMenuItem(self, tools_menu):
         """
         Give the SongUsage plugin the opportunity to add items to the