Fix uncaught exception for group updates

[emmyoop]

resolves #8371

Problem

Uncaught exception when a group is updated when a model is also modified.

Solution

Prevent the exception

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc) or this PR has already received feedback and approval from Product or DX
• This PR includes type annotations for new and modified functions

[github-actions]

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[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (d912654) 86.62% compared to head (c7c4d4a) 86.43%.
Report is 37 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8792      +/-   ##
==========================================
- Coverage   86.62%   86.43%   -0.19%     
==========================================
  Files         176      176              
  Lines       25663    26029     +366     
==========================================
+ Hits        22230    22499     +269     
- Misses       3433     3530      +97     

Flag	Coverage Δ
integration	83.23% <100.00%> (-0.21%)	⬇️
unit	64.84% <0.00%> (-0.29%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
core/dbt/contracts/graph/manifest.py	93.85% <100.00%> (+<0.01%)	⬆️

... and 45 files with indirect coverage changes

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