slackbridge_import command doesn't work

[antkaz]

Description:

After #11346 a slash command /slackbridge-import doesn't work.

Steps to reproduce:

1. Enable and setting a slackBridge
2. write the command /slackbridge-import

Expected behavior:

New messages imported

Actual behavior:

I got an error:
SlackBridge got an error while importing your messages at slack-bridge-dev: Cannot read property 'importMessages' of undefined

Server Setup Information:

• Version of Rocket.Chat Server: 2.4.0
• Operating System: macOS
• Deployment Method: local
• Number of Running Instances: 1
• DB Replicaset Oplog: enabled
• NodeJS Version: 8.7
• MongoDB Version: 4.0

Relevant logs:

I20200127-17:56:49.965(5)? Exception while invoking method 'slashCommand' TypeError: Cannot read property 'importMessages' of undefined
I20200127-17:56:49.966(5)?     at Object.SlackBridgeImport [as callback] (app/slackbridge/server/slackbridge_import.server.js:32:21)
I20200127-17:56:49.966(5)?     at Object._runningSlashCommand [as run] (app/utils/lib/slashCommand.js:28:42)
I20200127-17:56:49.966(5)?     at MethodInvocation.slashCommand (app/utils/lib/slashCommand.js:83:24)
I20200127-17:56:49.966(5)?     at maybeAuditArgumentChecks (packages/ddp-server/livedata_server.js:1771:12)
I20200127-17:56:49.966(5)?     at DDP._CurrentMethodInvocation.withValue (packages/ddp-server/livedata_server.js:719:19)
I20200127-17:56:49.966(5)?     at Meteor.EnvironmentVariable.EVp.withValue (packages/meteor.js:1234:12)
I20200127-17:56:49.966(5)?     at DDPServer._CurrentWriteFence.withValue (packages/ddp-server/livedata_server.js:717:46)
I20200127-17:56:49.966(5)?     at Meteor.EnvironmentVariable.EVp.withValue (packages/meteor.js:1234:12)
I20200127-17:56:49.966(5)?     at Promise (packages/ddp-server/livedata_server.js:715:46)
I20200127-17:56:49.966(5)?     at new Promise (<anonymous>)
I20200127-17:56:49.966(5)?     at Session.method (packages/ddp-server/livedata_server.js:689:23)
I20200127-17:56:49.966(5)?     at packages/ddp-server/livedata_server.js:559:43