fix(dbt): Validator error fix

[BoyuanZhangDE]

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable). If a new feature has been added a Usage Guide has been added for the same.
• For any breaking change/potential downtime/deprecation/big changes an entry has been made in Updating DataHub

[BoyuanZhangDE]

If the user doesn't input any item in the list ["manifest_path", "catalog_path", "sources_path"], this line of code will report an error: if values.get(f, "").startswith("s3://")
Fix this issue to first check if values.get(f, "") returns none then check if it starts with "s3://"

[github-actions]

Unit Test Results (build & test)

381 tests  ±0   381 ✔️ ±0   3m 1s ⏱️ ±0s
  89 suites ±0       0 💤 ±0 
  89 files   ±0       0 ❌ ±0 

Results for commit 3bff233. ± Comparison against base commit 6302d32.

♻️ This comment has been updated with latest results.

[github-actions]

Unit Test Results (metadata ingestion)

       5 files  ±0         5 suites  ±0   1h 30m 12s ⏱️ - 10m 22s
   555 tests ±0     552 ✔️ +1    3 💤 ±0  0 ❌  - 1 
2 552 runs  ±0  2 477 ✔️ +1  75 💤 ±0  0 ❌  - 1 

Results for commit 6356925. ± Comparison against base commit 09fc506.

This pull request removes 14 and adds 14 tests. Note that renamed tests count towards both.

tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type0-bytes]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type1-boolean]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type10-timestamp-micros]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type11-timestamp-micros]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type12-time-micros]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type13-uuid]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type2-date]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type3-decimal]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type4-double]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type5-fixed]
…

tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type0-BytesTypeClass]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type1-BooleanTypeClass]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type10-TimeTypeClass]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type11-TimeTypeClass]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type12-TimeTypeClass]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type13-StringTypeClass]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type2-DateTypeClass]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type3-NumberTypeClass]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type4-NumberTypeClass]
tests.unit.test_iceberg ‑ test_iceberg_map_to_schema_field[iceberg_type5-FixedTypeClass]
…

♻️ This comment has been updated with latest results.

code change addresses the changes requested