Fix unlikely but possible race in `WeakValueDictionary` It may happen that value in `valueArray` could have been already collected by the GC but #clearDeadSlots have not yet been called. When this happened, `#at:ifAbsentPut:` returned tombstone rather than updating the dictionary with value from block. This commit fixes this by checking whether `valueArray` contain the tombstone and if so, clearing up the dead slots and restarting the operation. HTH.

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LIBRARY libbasic

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DESCRIPTION     'Smalltalk/X Basic classes'

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VERSION         3.5

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CODE            EXECUTE READ 

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DATA            READ WRITE

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SECTIONS

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    INITCODE    READ EXECUTE 

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    INITDATA    READ WRITE 

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EXPORTS 

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    _libbasic_Init