fix(kepler) blank layer when no deck layers

[chrisgervang]

For #157.

Test

• Open kepler-integration example, delete all layers, attempt to export video.
• Also should work when all layers are just "unseen"

[coveralls]

Pull Request Test Coverage Report for Build 1247366727

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 26.641%

---

Totals
Change from base Build 1247350731:	0.0%
Covered Lines:	217
Relevant Lines:	708

---

💛 - Coveralls

[igorDykhta]

Works as expected

[coveralls]

Pull Request Test Coverage Report for Build 1247366727

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 26.641%

---

Totals
Change from base Build 1247350731:	0.0%
Covered Lines:	217
Relevant Lines:	708

---

💛 - Coveralls