Allow for CANONICAL_ROOT env var to be undefined
Allow for CANONICAL_ROOT env var to be undefined

The variable existence check was meant for runtime, and it causes
incomplete builds as Jekyll fails at build time, when the variable is
actually not defined (it's meant to be declared at runtime).

fabschurt/website,fabschurt/website,fabschurt/cv,fabschurt/cv,fabschurt/cv,fabschurt/cv,fabschurt/website