Error while publishing the Subflow in flow designer

[Manoj52]

When trying to publish my flow an error is poped stating 

Error : Cannot invoke "com.glide.flow.model.PharmacyCompound.getPrescription()" because the return value of "java.util.Map.get(Object)" is null.

Does any one faced this issue and knows how to resolve it ?

Thanks in Advance

[John Palmer]

Seeing the same error myself when a scheduled flow RUNS, after updating and publishing an Action with a Send Email that didn't like the data pill reference I dragged into the email body sectin (showed it as {{number}} rather thant the data pill name....

[vahini]

I got the same error, and i checked all the steps some fields are replaced with $ {{number............}} , removed these from payload , it got fixed. 

[John Palmer]

and this :
https://www.servicenow.com/community/developer-forum/cannot-able-to-activate-flow/m-p/3048354
at the bottom after clickng More.. mentiions an invalid data pill reference as their issue.