correctly handle empty <description> tags in hw_commands and fsw_commands

[dandelany]

Related to NASA-AMMOS/aerie#1466

Kind of a devious bug related to destructuring, you'd expect Typescript to complain about something like this, because myCollection.things can be undefined:

interface ThingCollection {
  things?: Array<Thing>
}
const myCollection: ThingCollection = getThingCollection();
const [thing] = myCollection.things;

... but this compiles and throws a runtime error. Might be good to do a scan for any other similar bugs before merging.

[goetzrrGit]

LGTM

We probably should bump the version to 1.0.6, as we are using 1.0.5 right now.

[dandelany]

Thanks - bumped the version. Also sneaked in one more edge-case fix in e14cb2d - this case already threw an error, its now more descriptive. Merging this & I will publish 1.0.6 on NPM also.