Issue with Jinja templates and max generations

[GeBo1]

With Enable Jinja2 templates and Combinatorial generation checked, setting Max generations to 0 raises an exception trying to call range(0) on this line:

prompts = [jinja_template.render(**self._context) for i in range(num_prompts)]

Setting Max generations to 1 works around the issue (which I'm not sure is intended or not).

This should make 0 behave as expected:

prompts = [jinja_template.render(**self._context) for i in range(num_prompts or 1)]