more efficient mass unsharing

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

@@ -540,16 +540,16 @@ class MainFrameModel {
         runInsideUIAsync {
             synchronized (allSharedFiles) {
                 allSharedFiles.removeAll(e.unsharedFiles)
+                shared.retainAll(allSharedFiles)
             }
             loadedFiles = allSharedFiles.size()
             
             for (SharedFile sharedFile : e.unsharedFiles) {
-                boolean wasVisible = shared.remove(sharedFile)
 
                 DefaultMutableTreeNode dmtn = fileToNode.remove(sharedFile)
-                if (dmtn != null) {
+                if (dmtn == null)
+                    continue
 
-                    if (wasVisible) {
                 Object[] path = dmtn.getUserObjectPath()
                 DefaultMutableTreeNode otherNode = treeRoot
                 for (int i = 1; i < path.length; i++) {
@@ -573,7 +573,6 @@ class MainFrameModel {
                     } else
                         break
                 }
-                    }
 
                 List<File> unshared = new ArrayList<>()
                 while (true) {
@@ -595,7 +594,6 @@ class MainFrameModel {
                     core.eventBus.publish(new DirectoryUnsharedEvent(directory: unsharedRoot))
                 }
             }
-            }
             
             view.refreshSharedFiles()
         }