Fix deserialization of Series in case of no values.

[JEnoch]

Description

Fix deserialization of Series in case of no values. Fix #74

Checklist

• Formatted code using cargo fmt --all
• Linted code using clippy cargo clippy --all-targets --all-features -- -D warnings
• Updated README.md using cargo readme -r influxdb -t ../README.tpl > README.md
• Reviewed the diff. Did you leave any print statements or unnecessary comments?
• Any unfinished work that warrants a separate issue captured in an issue with a TODO code comment

[Empty2k12]

Hey. Thanks for this code change.

Seems like you're running into a lot of edge-cases that have not been found yet. I am very grateful for your help in fixing those and would like to apologize for this.

Merging now!

[Empty2k12]

I am not sure when I will be able to release this. Would you be comfortable using the Git version for now until we're sure that there are no other problems you're running into that should make it into a release?

[JEnoch]

Sure, that's what I just did here: eclipse-zenoh/zenoh@00e23a7 .
I'm done with the integration of InfluxDB into zenoh for now, so I probably won't find new issues in the next weeks.
But zenoh users might... 😉
Anyhow, we won't need for a new influxdb-rust release before our final 0.5.0 release, which won't happen before end of 2020.

[Empty2k12]

Hello! I just published a change to crates.io containing your change as version 0.4.0. Thanks again for your contribution!