Generate less useless messages on and around the bridge

h/js/plugin/bridge.coffee

@@ -154,6 +154,7 @@ class Annotator.Plugin.Bridge extends Annotator.Plugin
       this._parse a for a in annotations when @cache[a.tag]
       # Then collect the new ones
       annotations = (this._parse a for a in annotations when not @cache[a.tag])
+      if annotations.length
         @annotator.loadAnnotations annotations
     )
 
@@ -240,9 +241,11 @@ class Annotator.Plugin.Bridge extends Annotator.Plugin
       scope: scope
       onReady: =>
         options.onConnect.call @annotator, source, origin, scope
+        annotations = (this._format a for t, a of @cache)
+        if annotations.length
           channel.notify
             method: 'loadAnnotations'
-          params: (this._format a for t, a of @cache)
+            params: annotations
 
     channel = this._build options