Coerce null/undefined to empty string when escaping

[emma-borhanian]

When you use escape tags with a null value it will be turned into the string "null", which can be incredibly inconvenient.

For example

value: "<%- null %>"

becomes

value: "null"

This patch changes the result to:

value: ""

This is consistent with the behavior of e.g. erb

[jfredett]

:+1: this effects my project as well, and would be a very convenient change

[fxposter]

Why not extract the escaping function and put it with the print one? It would be better to have one function instead of a lot of the same ones.

[emma-borhanian]

I was planning on making a follow-up pull request to perform that optimization, and also apply it to the "escape_function" at the same time.

Unfortunately it looks like this project is dead.