Setting defaultTemplate breaks slide formatting

[jtuttle]

Describe the bug
When trying to use a template through the defaultTemplate frontmatter, it completely breaks slide formatting. The slides all get squished together and other artifacts occur (see the empty bullets in the second screenshot below). It's like the template is being applied to all of the slides lumped together instead of to each individual slide.

The templating appears to work fine when setting individual slides using <!-- slide template="[[simple-template]]" -->, which I believe rules out the template as the culprit.

Slides with individual templates defined (works):

Slides after setting defaultTemplate (does not work):

Samples to Reproduce
Steps & Examples to reproduce the behavior:

presentation.md

---
margin: 0
defaultTemplate: "[[simple-template]]"
---
---
## Slide One

---
## Slide Two

simple-template

<% content %>

footer content

Expected behavior
The template should be applied to all slides without slide formatting breaking.