Inconsistent null checks in ImmutableSortedMap

[johnsoneal]

When creating ImmutableSortedMap instances the documentation for methods copyOf and copyOfSorted state:

"NullPointerException - if any key or value in map is null"

However this behavior is not consistent an it is possible to create a map with null values.

Given a HashMap of stings with map:{a:null} all the copOf methods throw as expected, with a map:{a:null, b:two} then none of the copyOf methods throw.

Given a SortedMap of strings with map:{a:null} and a natural order copyOf and copyOfSorted all throw as expected; with a map:{a:null, b:two} then copyOf(Map) and copyOfSorted(SortedMap) throw; copyOf(Iterable), copyOf(Iterable, Comparator), copyOf(Map, Comparator) do not throw; with a map:{a:one, b:null}
copyOf and copyOfSorted all throw as expected.

From what I can tell this behavior is only present for maps with two elements and only when the null is the first value of the first key. The of and builder methods are not effected an throw as expected.

[cpovirk]

Nice catch. Likely the problem is in the else case of fromEntries.

[cpovirk]

9bcedd8