SkipList: Searching in a list with empty pages not possible

[MarcusDenker]

If we remove all entries in a page, we can not use find:

See this test:

testRemoveAllFromPageAndFind
    | entries return |
    "We test that after removing all entries from one page, #nextAssociation will continue to the next page"

    index keySize: 1016. "huge keySize forces multiple pages"
    entries :=  #(104 247 56 281 61 286 66 337 308 1 400 272 347 335 45 62 207 7 123 140).

    entries do: [:toAdd |
        index at: toAdd  put: #[ 1 2 3 4 5 6 7 8 ] ].

    "can we find all the keys we added?"
    entries do: [:each | self assert: (index at: each ) equals: #[ 1 2 3 4 5 6 7 8 ]].
    "#values iterates using #basicNextAssociation"
    self assert: index values size equals: entries size.

    index removeKey: 247.
    index removeKey: 272.
    self assert: (index pageAt: 3) isEmpty.
    self assert: index values size equals: entries size - 2.

    "We can search for a key that is in a page after the empty page"    
    return := index newIterator 
        find: 281.
    self assert: return notNil

The reason is that SoilSkipListIterator>>#findPageFor: uses #smallestKey

[MarcusDenker]

pages should never be empty