Ensure that all environment variable calls are properly handled

[Silvyre]

Since our CI testing does not define any of the environment variables that we set locally via our .env file, calls to any such variables (e.g. process.env.BLOG_INACTIVE_TIME) will return undefined during CI testing. As such, environment variables should always be accompanied by a default value.

For example, replacing process.env.BLOG_INACTIVE_TIME with (process.env.BLOG_INACTIVE_TIME || 365) effectively provides a default value of 365 to that environment variable.

Every instance of environment variables usage within our codebase should be reviewed to ensure that we are able to account for cases where those variables may be undefined.

In select cases, when an environment variable is undefined, it may be prudent to take further action (in addition to falling back on default value): logging a warning, throwing an error, etc.