Here's what's going on:

In the code, it assumes that either:

1. The pump flow rate was autosized and the autosized rated flow rate is available in the SQL file for this pump, which means that a sizing run has been done already.
2. The pump flow rate was hard sized.

The code needs to be modified to throw a better, more explanatory error when neither of these conditions are met.

You can run a sizing run using OpenStudio-Standards in your measure via:

model.runSizingRun()