Panic in `Unit.Module.Graph` with `ExplicitLevelImports` when using `do` notation without `Monad Q` imported as `splice`
## Summary
When compiling the module `X.hs`
```
{-# LANGUAGE ExplicitLevelImports, TemplateHaskell, NoImplicitPrelude #-}
module X where
x = $(do
_ <- _
_)
```
I get
```
<no location info>: error:
panic! (the 'impossible' happened)
GHC version 9.15.20251112:
expectJust
Call stack:
CallStack (from HasCallStack):
pprPanic, called at compiler/GHC/Data/Maybe.hs:77:19 in ghc-9.15-inplace:GHC.Data.Maybe
expectJustError, called at compiler/GHC/Data/Maybe.hs:74:24 in ghc-9.15-inplace:GHC.Data.Maybe
expectJust, called at compiler/GHC/Unit/Module/Graph.hs:577:8 in ghc-9.15-inplace:GHC.Unit.Module.Graph
Please report this as a GHC bug: https://www.haskell.org/ghc/reportabug
```
## Steps to reproduce
compile the listed module `X` with `ghc` HEAD
## Expected behavior
This should probably emit a level error about `Monad Q` not being in scope for the current level.
## Environment
* GHC version used: ghc HEAD at 8b080e048d51defa19fe9a484ec922b880a22a8b
Optional:
* Operating System: NixOS
* System Architecture: x86_64
issue