If you write a malformed {{#if}} helper with too many arguments, you get weird syntax errors that are different depending on just how you malformed the helper:

{{#if anything_goes_here "string"}}

cannot read property 'includeZero' of undefined

{{#if anything_goes_here undefined}}

Cannot read property 'hash' of undefined

{{#if anything_goes_here null}}

Cannot read property 'hash' of null

Here's a JS Fiddle demonstrating these errors
https://jsfiddle.net/m5a9q3b0/3/

Obviously, the if statement examples are incorrect, but the varied weird errors that get generated are the problem. In Ghost themes we regularly see all 3 of these errors, and it's clear noone understands what they mean or how to fix them.

We just added an ugly workaround to Ghost you can see here