Fix a myriad of problems with the ACP/Plugins page

- Fixed #3350
- Fixed issue where the normalised API return would have the wrong id for all plugins
- Fixed issue where uninstalling a locally installed plugin via ACP would cause NodeBB to crash
- Simplified ACP/Plugins client-side code to simply refresh the page after installing or uninstalling a plugin.

public/src/admin/extend/plugins.js

@@ -186,22 +186,7 @@ define('admin/extend/plugins', function() {
 				return app.alertError(err.message);
 			}
 
-			var targetList = (pluginData.installed ? 'installed' : 'download'),
-				otherList = (pluginData.installed ? 'download' : 'installed'),
-				payload = {};
-
-			payload[targetList] = pluginData;
-			templates.parse('admin/partials/' + targetList + '_plugin_item', payload, function(html) {
-				var pluginList = $('ul.' + targetList);
-
-				pluginList.append(html);
-				$('ul.' + otherList).find('li[data-plugin-id="' + pluginID + '"]').slideUp('slow', function() {
-					$(this).remove();
-					$('html,body').animate({
-						scrollTop: pluginList.find('li').last().offset().top - 48
-					}, 1000);
-				});
-			});
+			ajaxify.refresh();
 
 			app.alert({
 				alert_id: 'plugin_toggled',

src/plugins.js

@@ -170,9 +170,13 @@ var fs = require('fs'),
 		require('request')(url, {
 			json: true
 		}, function(err, res, body) {
+			if (res.statusCode === 404 || !body.payload) {
+				return callback(err, {});
+			}
+
 			Plugins.normalise([body.payload], function(err, normalised) {
 				normalised = normalised.filter(function(plugin) {
-					return plugin.id = id;
+					return plugin.id === id;
 				});
 				return callback(err, !err ? normalised[0] : undefined);
 			});