Autocompleter throws exception for global variable definition

[JakubLinhart]

 System.NullReferenceException: Object reference not set to an instance of an object.
   at InjectionScript.Runtime.DefinitionCollector.VisitGlobalVar(GlobalVarContext context) in c:\Users\jakub\sources\ultima\InjectionScript\src\InjectionScript\Runtime\DefinitionCollector.cs:line 44
   at InjectionScript.Parsing.Syntax.injectionParser.GlobalVarContext.Accept[TResult](IParseTreeVisitor`1 visitor) in c:\Users\jakub\sources\ultima\InjectionScript\src\InjectionScript\obj\Debug\net46\injectionParser.cs:line 290
   at Antlr4.Runtime.Tree.AbstractParseTreeVisitor`1.VisitChildren(IRuleNode node)
   at InjectionScript.Parsing.Syntax.injectionBaseVisitor`1.VisitFileSection(FileSectionContext context) in c:\Users\jakub\sources\ultima\InjectionScript\src\InjectionScript\obj\Debug\net46\injectionBaseVisitor.cs:line 57
   at InjectionScript.Parsing.Syntax.injectionParser.FileSectionContext.Accept[TResult](IParseTreeVisitor`1 visitor) in c:\Users\jakub\sources\ultima\InjectionScript\src\InjectionScript\obj\Debug\net46\injectionParser.cs:line 225
   at Antlr4.Runtime.Tree.AbstractParseTreeVisitor`1.VisitChildren(IRuleNode node)
   at InjectionScript.Parsing.Syntax.injectionBaseVisitor`1.VisitFile(FileContext context) in c:\Users\jakub\sources\ultima\InjectionScript\src\InjectionScript\obj\Debug\net46\injectionBaseVisitor.cs:line 46
   at InjectionScript.Parsing.Syntax.injectionParser.FileContext.Accept[TResult](IParseTreeVisitor`1 visitor) in c:\Users\jakub\sources\ultima\InjectionScript\src\InjectionScript\obj\Debug\net46\injectionParser.cs:line 159
   at InjectionScript.Runtime.InjectionRuntime.Load(String content, String fileName) in c:\Users\jakub\sources\ultima\InjectionScript\src\InjectionScript\Runtime\InjectionRuntime.cs:line 50
   at InjectionScript.Lsp.Completer.GetCompletions(String fileContent, Int32 line, Int32 column) in c:\Users\jakub\sources\ultima\InjectionScript\src\InjectionScript.Lsp\Completer.cs:line 105
   at InjectionScript.Lsp.Server.CompletionHandler.Handle(CompletionParams request, CancellationToken cancellationToken) in c:\Users\jakub\sources\ultima\InjectionScript\src\InjectionScript.Lsp.Server\CompletionHandler.cs:line 39
   at OmniSharp.Extensions.LanguageServer.Server.Pipelines.ResolveCommandPipeline`2.Handle(TRequest request, CancellationToken cancellationToken, RequestHandlerDelegate`1 next) in C:\projects\csharp-language-server-protocol\src\Server\Pipelines\ResolveCommandPipeline.cs:line 37
   at OmniSharp.Extensions.LanguageServer.Server.LspRequestRouter.RouteRequest(IHandlerDescriptor descriptor, Request request) in C:\projects\csharp-language-server-protocol\src\Server\LspRequestRouter.cs:line 163