When, under certain conditions, a compiled template fails to execute, the including (parent) template will simply use an empty string.
If this template is part of view-cache or cache-block, it's (invalid) contents will still be cached.

The conditions that lead to the compiled template execution failing are not easily reproducible, but may derive - for instance - from APC (Alternative Php Cache) inclusion optimizer (apc.include_once_override).

In this situation, the caches should NOT be generated/saved. A fatal error (exception) could be thrown instead.