Fix exception when version is missing when installing from the Hub package index

[dbeatty10]

resolves #10048

Problem

When version is missing, it raises an exception that spits out an ugly stacktrace.

This is because the Python here will fail when version is completely missing:

dbt-core/core/dbt/contracts/project.py

Line 119 in bcbde3a

if not package["version"]:

It looks like the tests in the original implementation (#5812) weren't covering this case.

Solution

Allow it to be completely missing so we can raise the appropriate error message.

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
• 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)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.16%. Comparing base (bcbde3a) to head (63c6dad).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10049      +/-   ##
==========================================
- Coverage   88.22%   88.16%   -0.06%     
==========================================
  Files         181      181              
  Lines       22643    22643              
==========================================
- Hits        19976    19963      -13     
- Misses       2667     2680      +13     

Flag	Coverage Δ
integration	85.46% <100.00%> (-0.13%)	⬇️
unit	62.31% <100.00%> (ø)

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[jtcohen6]

@dbeatty10 Thank you, this is better!

(Future enhancement, out of scope here: if version is missing, assume it means "unbounded," the same as >=0.0.1)