compactAdd doesn't work with SmallArray#

I get this when I try to compact a small array:

internal error: stg_compactAddWorkerzh: TODO: SMALL_MUT_ARR_PTRS
    (GHC version 8.2.0.20170404 for x86_64_unknown_linux)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

If I look in rts/Compact.cmm, I can see that this hasn't been implemented. I haven't seen this in another issue, so I just wanted to make sure it was not overlooked before the 8.2 release.

Trac metadata

Trac field	Value
Version	8.2.1-rc2
Type	Bug
TypeOfFailure	OtherFailure
Priority	high
Resolution	Unresolved
Component	Runtime System
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