Save channel as array for incoming integration always

packages/rocketchat-integrations/server/methods/incoming/addIncomingIntegration.coffee

@@ -69,6 +69,7 @@ Meteor.methods
 
 		integration.type = 'webhook-incoming'
 		integration.token = token
+		integration.channel = channels
 		integration.userId = user._id
 		integration._createdAt = new Date
 		integration._createdBy = RocketChat.models.Users.findOne @userId, {fields: {username: 1}}

server/startup/migrations/v079.js

+RocketChat.Migrations.add({
+	version: 79,
+	up: function() {
+		const integrations = RocketChat.models.Integrations.find({type: 'webhook-incoming'}).fetch()
+
+		for (const integration of integrations) {
+			if (typeof integration.channel === 'string') {
+				RocketChat.models.Integrations.update({_id: integration._id}, {
+					$set: {
+						channel: integration.channel.split(',').map(channel => channel.trim())
+					}
+				});
+			}
+		}
+	}
+});