Crash of the LanguageServer in the Julia VS code extension

Bug Description:

The Julia VS Code extension installs correctly within Theia. However, when using it, the LanguageServer frequently crashes, due to requests looking like:

[Trace - 10:56:22 AM] Sending request 'julia/getModuleAt - (37)'.
Params: {
    "textDocument": {
        "uri": "file:///home/project/theia-jl/test.jl"
    },
    "version": 30,
    "position": {
        "_line": 11,
        "_character": 0
    }
}

instead of the expected

[Trace - 10:56:22 AM] Sending request 'julia/getModuleAt - (37)'.
Params: {
    "textDocument": {
        "uri": "file:///home/project/theia-jl/test.jl"
    },
    "version": 30,
    "position": {
        "line": 11,
        "character": 0
    }
}

Steps to Reproduce:

1. Run Theia from the theia-full docker image
2. install Julia inside the docker container
   • see comment below for a Dockerfile automating this step
3. install the Julia VS code extension (from the open VSX registry)
4. open any Julia file and start typing some code, hovering over keywords...
   • see comment below for an example Julia source file
5. the LanguageServer should crash pretty quickly

Additional Information

• Operating System: Ubuntu
• Theia Version: Theia Multi-Language Example @theia/callhierarchy 1.5.0 @theia/console 1.5.0 @theia/core 1.5.0 @theia/cpp-debug 1.0.0 @theia/debug 1.5.0 @theia/editor 1.5.0 @theia/editor-preview 1.5.0 @theia/file-search 1.5.0 @theia/filesystem 1.5.0 @theia/getting-started 1.5.0 @theia/git 1.5.0 @theia/keymaps 1.5.0 @theia/markers 1.5.0 @theia/messages 1.5.0 @theia/metrics 1.5.0 @theia/mini-browser 1.5.0 @theia/monaco 1.5.0 @theia/navigator 1.5.0 @theia/outline-view 1.5.0 @theia/output 1.5.0 @theia/plugin-ext 1.5.0 @theia/plugin-ext-vscode 1.5.0 @theia/preferences 1.5.0 @theia/preview 1.5.0 @theia/process 1.5.0 @theia/scm 1.5.0 @theia/scm-extra 1.5.0 @theia/search-in-workspace 1.5.0 @theia/task 1.5.0 @theia/terminal 1.5.0 @theia/typehierarchy 1.5.0 @theia/userstorage 1.5.0 @theia/variable-resolver 1.5.0 @theia/vsx-registry 1.5.0 @theia/workspace 1.5.0