Cannot read property 'original' of undefine
Cannot read property 'original' of undefine

In this very special case the linter run fails with following exception:

```
TypeError: Cannot read property 'original' of undefined
    at BasePlugin.BlockIndentation.validateBlockChildren (/Users/michal/PuppetLabs/ember-template-lint/lib/rules/lint-block-indentation.js:249:31)
    at BasePlugin.BlockIndentation.process (/Users/michal/PuppetLabs/ember-template-lint/lib/rules/lint-block-indentation.js:118:10)
    at BasePlugin.ElementNode (/Users/michal/PuppetLabs/ember-template-lint/lib/rules/lint-block-indentation.js:109:14)
    at /Users/michal/PuppetLabs/ember-template-lint/lib/rules/base.js:290:21
    at visitNode (glimmer-syntax/lib/traversal/traverse.ts:13:28)
    at visitArray (glimmer-syntax/lib/traversal/traverse.ts:74:18)
    at visitKey (glimmer-syntax/lib/traversal/traverse.ts:56:5)
    at visitNode (glimmer-syntax/lib/traversal/traverse.ts:30:7)
    at Object.traverse (glimmer-syntax/lib/traversal/traverse.ts:113:3)
    at BasePlugin.transform (/Users/michal/PuppetLabs/ember-template-lint/lib/rules/base.js:76:17)
    at Object.preprocess (glimmer-syntax/lib/parser.ts:32:25)
    at precompile (glimmer-compiler/lib/compiler.ts:63:13)
    at Linter.verify (/Users/michal/PuppetLabs/ember-template-lint/lib/index.js:95:7)
    at verify (test/helpers/rule-test-harness.js:18:21)
    at Context.<anonymous> (test/helpers/rule-test-harness.js:59:22)
    at callFn (/Users/michal/PuppetLabs/ember-template-lint/node_modules/mocha/lib/runnable.js:345:21)
    at Test.Runnable.run (/Users/michal/PuppetLabs/ember-template-lint/node_modules/mocha/lib/runnable.js:337:7)
    at Runner.runTest (/Users/michal/PuppetLabs/ember-template-lint/node_modules/mocha/lib/runner.js:444:10)
    at /Users/michal/PuppetLabs/ember-template-lint/node_modules/mocha/lib/runner.js:550:12
    at next (/Users/michal/PuppetLabs/ember-template-lint/node_modules/mocha/lib/runner.js:361:14)
    at /Users/michal/PuppetLabs/ember-template-lint/node_modules/mocha/lib/runner.js:371:7
    at next (/Users/michal/PuppetLabs/ember-template-lint/node_modules/mocha/lib/runner.js:295:14)
    at /Users/michal/PuppetLabs/ember-template-lint/node_modules/mocha/lib/runner.js:334:7
    at done (/Users/michal/PuppetLabs/ember-template-lint/node_modules/mocha/lib/runnable.js:295:5)
    at callFn (/Users/michal/PuppetLabs/ember-template-lint/node_modules/mocha/lib/runnable.js:363:7)
    at Hook.Runnable.run (/Users/michal/PuppetLabs/ember-template-lint/node_modules/mocha/lib/runnable.js:337:7)
    at next (/Users/michal/PuppetLabs/ember-template-lint/node_modules/mocha/lib/runner.js:309:10)
    at Immediate.<anonymous> (/Users/michal/PuppetLabs/ember-template-lint/node_modules/mocha/lib/runner.js:339:5)
    at runCallback (timers.js:649:20)
    at tryOnImmediate (timers.js:622:5)
    at processImmediate [as _immediateCallback] (timers.js:594:5
```

Conditions observed:
 - The problem seems to be badly indented comment after `if` or `unless` (any pair?) statement
 - The code has to be nested in some other element - `div` in my example

rwjblue/ember-template-lint