Partial block behavior differences from original implementation

[garyemerson]

(Thanks for writing this library btw! I'm starting to use it quite a lot on my website.)

I found a behavior difference compared with the original javascript implementation. With the original implementation, using a partial that doesn't exist will cause an error. Also, using a partial before its definition works fine.

With handlebars-rust, using a partial that doesn't exist will silently render as empty (even in strict mode). Using a partial before its definition will also silently render as empty.

Here's an example template that showcases these behaviors (javascript implementation playground link):

before
{{> foo}}
{{> bar}}
after

{{#*inline "foo"}}
foo
{{/inline}}

[sunng87]

Thank you @garyemerson I will look into this issue later today. If there is a difference we will align behaviour with original javascript version