for is not behaving properly (as defined by Ruby's liquid) when a value is null.

[ebobby]

When rendering the following, with strict: true:

{% assign hello = "hello,world" | split: "," | concat: null %}{% for i in hello %}{{ i }}{% endfor %}

It returns an error undefined variable: i which seems to be a bug, given that the variable is defined, just happens to be null. This is a mismatch with the behavior of Shopify's liquid.