Mail quits and quits - not even time to report

This just started today and only occurs with my iMac running High Sierra - the report comes up saying "Mail quit unexpectedly while using the HockeySDK plug-in"

PlugIn Path: /Users/USER/Library/Mail/*/HockeySDK.framework/Versions/A/HockeySDK

PlugIn Identifier: net.hockeyapp.sdk.mac

PlugIn Version: 4.1.3 (60)

I don't know what this means but want to get it fixed.