Case expression with Array.popFirst and redundant branches

The code:

module Bug exposing ( .. )

err : Array Int -> Int
err array =
    case Array.popFirst array of
        Nothing -> 0
        Just { first = _, rest = _ } -> 0
        _ -> 0

The error:

Compiling ...gren: Map.!: given key is not an element in the map
CallStack (from HasCallStack):
  error, called at libraries/containers/containers/src/Data/Map/Internal.hs:617:17 in containers-0.6.7:Data.Map.Internal

-- ERROR -----------------------------------------------------------------------

I ran into something that bypassed the normal error reporting process! I
extracted whatever information I could from the internal error:

>   thread blocked indefinitely in an MVar operation
...

It compiles without the last branch. Without the first branch it also compiles. But it seems to have problems with the redundant branches. If I remove the Array.popFirst, it also compiles.

Start by compiling the Gren reproducer and compare it with the variants that remove the final branch, the first branch, or Array.popFirst. Trace the compiler path handling the case expression and redundant branches. Done means the original example compiles without the internal Map.! or blocked-MVar error.