is-array? throws exception on nil in clj

[timothypratley]

A minor annoyance that causes an downstream issue:
(d/conn-from-datoms (d/datoms @*conn :eavt) schema) will fail on an empty database.
This is the recommended way to update a schema from DataScript documentation.
This in turn can be easily worked around by only using conn-from-datoms for non-nil.

However type checks typically shouldn't throw exceptions, so submitting a patch.

[tonsky]

Thank you! Just pushed DataScript 1.2.1

[timothypratley]

Thank you :)