Uncaught exception Cannot call null (reproducible!)

So far I failed to reproduce this outside VSCode, but it is 100% reproducible inside it. Might have something to do with `--cwd` calls because of the weird `changed directories: []` below.

`Main.hx`
```haxe
class Main {
static function main() {
Macro.func();
}
}
```

`Macro.hx`
```haxe
class Macro {
public static macro function func() {
var t = haxe.macro.Context.getType("Int");
trace(t);
return macro 1;
}
}
```

`build.hxml`
```hxml
-main Main
-js main.js
```

`.vscode/settings.json`
```json
{
"haxe.displayServer": {"arguments": ["-v"]},
"haxe.buildCompletionCache": false,
"haxe.enableDiagnostics": false
}
```
(so the amount of uncontrolled server calls is minimal)

1) Open this project in VSCode
2) Compile with the build task (so cache server is used)
3) Comment line 3 in `Macro.hx` (`var t = haxe.macro.Context.getType("Int");`) and save the file
4) Compile with the build task again - get the proper error (`Unknown identifier : t`)
5) Uncomment line 3 in `Macro.hx` back and save the file
6) Compile with the build task - BAM: `Macro.hx:3: characters 17-50 : Uncaught exception Cannot call null`

Haxe server output

```
Haxe language server started
Using --server-connect
Haxe connected!
Processing Arguments [--display,{"jsonrpc":"2.0","id":0,"method":"initialize","params":{"supportsResolve":true,"exclude":["zpp_nape"],"maxCompletionItems":1000}}]
Completion Response =
{"jsonrpc":"2.0","id":0,"result":{"result":{"methods":["display/definition","server/contexts","server/moduleCreated","server/invalidate","server/module","server/files","initialize","display/completion","typer/compiledTypes","display/references","server/modules","server/memory/context","display/completionItem/resolve","display/typeDefinition","server/memory","display/implementation","display/hover","display/package","display/signatureHelp","server/memory/module","server/readClassPaths","server/configure"],"haxeVersion":{"major":4,"minor":1,"patch":0,"pre":"rc.1","build":"bc6eca1fd"},"protocolVersion":{"major":0,"minor":4,"patch":0}},"timestamp":1582399821.6802447}}
Stats = 0 files, 0 classes, 0 methods, 0 macros
Time spent : 0.000s
Listening on port 6000
Processing Arguments [--display,{"jsonrpc":"2.0","id":1,"method":"server/configure","params":{"noModuleChecks":true,"print":{"completion":false,"reusing":false},"legacyCompletion":false}}]
Stats = 0 files, 0 classes, 0 methods, 0 macros
Time spent : 0.000s
Client connected
Processing Arguments [--cwd,c:\Users\nadako\Code\playground,build.hxml]
Defines dce=std,haxe3=1,haxe4=1,haxe=4.1.0-rc.1,haxe_ver=4.100,js-es5=1,js=1,js_es5=1,js_es=5,source-header=Generated by Haxe 4.1.0-rc.1+bc6eca1fd,target.name=js,target.unicode=true,target.utf16=true,true=1,utf16=1
Using signature 84fef1af5de52a14c9c1eb15ad163b2e
Display position: ?: -1--1
0, js: Cached 48 modules
Stats = 158 files, 171 classes, 862 methods, 1 macros
Time spent : 0.150s
Client disconnected
Processing Arguments [--display,{"jsonrpc":"2.0","id":2,"method":"server/invalidate","params":{"file":"c:/Users/nadako/Code/playground/Macro.hx"}}]
Stats = 0 files, 0 classes, 0 methods, 0 macros
Time spent : 0.000s
Client connected
Processing Arguments [--cwd,c:\Users\nadako\Code\playground,build.hxml]
Defines dce=std,haxe3=1,haxe4=1,haxe=4.1.0-rc.1,haxe_ver=4.100,js-es5=1,js=1,js_es5=1,js_es=5,source-header=Generated by Haxe 4.1.0-rc.1+bc6eca1fd,target.name=js,target.unicode=true,target.utf16=true,true=1,utf16=1
Using signature 84fef1af5de52a14c9c1eb15ad163b2e
Display position: ?: -1--1
0, js: skipping Main(Macro)
0, js: skipping Macro
1,evl: skipping Macro
> Macro.hx:4: characters 15-16 : Unknown identifier : t
Macro.hx:4: characters 15-16 : For function argument 'v'
1,evl: found 35 directories
0, js: found 41 directories
Stats = 2 files, 3 classes, 2 methods, 1 macros
Time spent : 0.030s
Client disconnected
Processing Arguments [--display,{"jsonrpc":"2.0","id":3,"method":"server/invalidate","params":{"file":"c:/Users/nadako/Code/playground/Macro.hx"}}]
Stats = 0 files, 0 classes, 0 methods, 0 macros
Time spent : 0.000s
Client connected
Processing Arguments [--cwd,c:\Users\nadako\Code\playground,build.hxml]
Defines dce=std,haxe3=1,haxe4=1,haxe=4.1.0-rc.1,haxe_ver=4.100,js-es5=1,js=1,js_es5=1,js_es=5,source-header=Generated by Haxe 4.1.0-rc.1+bc6eca1fd,target.name=js,target.unicode=true,target.utf16=true,true=1,utf16=1
Using signature 84fef1af5de52a14c9c1eb15ad163b2e
Display position: ?: -1--1
0, js: changed directories: []
0, js: skipping Main(Macro)
0, js: skipping Macro
1,evl: changed directories: []
1,evl: skipping Macro
> Macro.hx:3: characters 17-50 : Uncaught exception Cannot call null
Main.hx:3: characters 3-15 : Called from here
> Main.hx:1: lines 1-5 : Defined in this class
Stats = 2 files, 3 classes, 2 methods, 1 macros
Client disconnected
Time spent : 0.005s
```

As mentioned, these `changed directories: []` look suspicious and if it is the cause, it might explain why it's so hard to reproduce as it might be related to current working directories.