fix regression: non array iterables were always treatead as empty

[antoinep92]

Issue #347 was fixed by @StorytellerCZ in PR #348, but the fix broke the rich error message (#each value display) for non-array iterables. This PR fixes that regression. The fix works as follow:

• we add a special case for displaying arrays, that's compatible with IE9+
• the iterable but not array case is unreachable under IE since, so we use Array.from there

[StorytellerCZ]

Thanks a lot @antoinep92 !
I will try to release this in the next two hours.