[BUG] Webdav source failes with "Unable to validate object" exception

[petermicuch]

Describe the bug
I have test webdav server from https://sabre.io/. I have created channel with "File Reader" as a Source and have selected webdav as a method. I have entered correct URL of the location from where I want to pull files from and hit "Test Read" button, which works fine and responds with Successfully connected to: webdav:https://...

However when I deploy this channel it throws below exception:

[2021-06-17 04:21:24,294]  ERROR  (com.mirth.connect.server.channel.ErrorTaskHandler:25): com.mirth.connect.donkey.server.StartException: Failed to start channel WebDavScrapping (ab7e18ba-e50b-4446-9ca0-f0e35fcf3316).

	at com.mirth.connect.donkey.server.channel.Channel.start(Channel.java:778)

	at com.mirth.connect.server.controllers.DonkeyEngineController$ChannelStatusTask.execute(DonkeyEngineController.java:2005)

	at com.mirth.connect.server.channel.ChannelTask.call(ChannelTask.java:67)

	at com.mirth.connect.server.channel.ChannelTask.call(ChannelTask.java:16)

	at java.base/java.util.concurrent.FutureTask.run(Unknown Source)

	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)

	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)

	at java.base/java.lang.Thread.run(Unknown Source)
Caused by: com.mirth.connect.donkey.server.ConnectorTaskException: Unable to validate object

	at com.mirth.connect.connectors.file.FileReceiver.onStart(FileReceiver.java:158)

	at com.mirth.connect.donkey.server.channel.SourceConnector.start(SourceConnector.java:104)

	at com.mirth.connect.donkey.server.channel.PollConnector.start(PollConnector.java:32)

	at com.mirth.connect.donkey.server.channel.Channel.start(Channel.java:754)

	... 7 more
Caused by: java.util.NoSuchElementException: Unable to validate object

	at org.apache.commons.pool2.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:506)

	at org.apache.commons.pool2.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:363)

	at com.mirth.connect.connectors.file.FileConnector.getConnection(FileConnector.java:186)

	at com.mirth.connect.connectors.file.FileReceiver.onStart(FileReceiver.java:153)

	... 10 more

Expected behavior
Channel shall be started and read files from webdav location that is accessible in the selected time intervals.

Actual behavior
There is above exception after channel is started.

Environment (please complete the following information):

• OS: Linux Docker - using image nextgenhealthcare/connect
• Java Distribution/Version openjdk:11
• Connect Version 3.11.0

Workaround(s)
n.a.