Cannot configure problemMatcher for User-Level Task

[tsmaeder]

Configuring a problemMatcher for user-level task when running the task fails silently

Steps to Reproduce:

1. Add the following task to the "user level" tasks.json

{
            "label": "Global Task",
            "type": "shell",
            "command": "foo"
}

2. Run the task
3. When asked for the problemMatcher, select "never scan the output for this task".
4. Observe: nothing happens.

The expectation here is that an empty problemMatcher array is added to the task like so:

{
            "label": "Global Task",
            "type": "shell",
            "command": "foo",
            "problemMatcher": []
}

This works in VS Code.

Additional Information

• Operating System: Windows/FF
• Theia Version: master < 1.2.0