R1:6124865c567e

Minor phutil_tag/HTML fixes

Summary:

- In stack traces, a `,` should clearly be a `.`.
- In Calendar, a 'td' got swapped with a 'p' somewhere.
- In old-style transaction views, strlen() is no longer a sufficient test.

Test Plan:

- Verified stack traces render correctly.
- Verified calendar renders correctly.
- Verified Maniphest transactions with no comment no longer have a little empty div a few pixels high.

Reviewers: chad

Reviewed By: chad

CC: aran

Differential Revision: https…