Leave the channel when a shared folder is removed from a drive

www/common/outer/sharedfolder.js

@@ -98,7 +98,7 @@ define([
 
         var parsed = Hash.parsePadUrl(href);
         var secret = Hash.getSecrets('drive', parsed.hash, data.password);
-        // If we don' have valid keys, abort and remove the proxy to make sure
+        // If we don't have valid keys, abort and remove the proxy to make sure
         // we don't block the drive permanently
         if (!secret.keys) {
             store.manager.deprecateProxy(id);

www/common/outer/userObject.js

@@ -168,6 +168,7 @@ define([
                     if (channelId) { toClean.push(channelId); }
                     if (exp.isSharedFolder(id)) {
                         delete files[SHARED_FOLDERS][id];
+                        if (config.removeProxy) { config.removeProxy(id); }
                     } else {
                         spliceFileData(id);
                     }