Request textDocument/hover failed.

### How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

### Which OS are you using?

MacOS

### What is the issue affecting?

Hover

### Expected Behaviour

no errors when hover

### Actual Behaviour

error popups when hover

[error][#0:script/vm/global.lua:640]: script/vm/global.lua:640: attempt to index a nil value (local 'source')
stack traceback:
script/vm/global.lua:640: in function 'vm.vm.getGlobalNode'
(...tail calls...)
script/vm/visible.lua:182: in field 'isVisible'
script/core/hover/table.lua:105: in upvalue 'getVisibleKeyMap'
script/core/hover/table.lua:188: in upvalue 'buildTable'
script/core/hover/label.lua:51: in function
(...tail calls...)
script/core/hover/init.lua:37: in local 'addHover'
script/core/hover/init.lua:92: in upvalue 'getHover'
script/core/hover/init.lua:144: in field 'byUri'
script/provider/provider.lua:368: in function <script/provider/provider.lua:346>
[C]: in global 'xpcall'
script/proto/proto.lua:202: in function <script/proto/proto.lua:177>

### Reproduction steps

```lua
---@alias namespace.B<T> A<T>

---@class namespace.C<T>
---@field _x T

---@class namespace.D<T>

---@class A<T>:namespace.C<T>,namespace.D<T>
local A = {}
```

hover on A

### Additional Notes

_No response_

### Log File

_No response_

Reproduce the failure by hovering over A in the Lua snippet, then start at script/vm/global.lua:640 and trace the calls through script/vm/visible.lua:182 and script/core/hover/table.lua:105. Done means the reported hover request produces no error popup and still returns the expected hover information for the reproduction.

Written by the indexing model from the issue text.