fix(SIP-68): handle empty table name during migration

[ktmud]

SUMMARY

This should fix #19421 (comment)

Reproduced and tested locally by manually setting a local physical SqlaTable to have empty table name:

update tables set table_name = '' where id = 1;

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

Merging #19793 (639ab5c) into master (5e468f7) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #19793   +/-   ##
=======================================
  Coverage   66.54%   66.54%           
=======================================
  Files        1692     1692           
  Lines       64775    64775           
  Branches     6661     6661           
=======================================
  Hits        43103    43103           
  Misses      19972    19972           
  Partials     1700     1700           

Flag	Coverage Δ
hive	52.85% <ø> (ø)
mysql	81.90% <ø> (ø)
postgres	81.95% <ø> (ø)
presto	52.70% <ø> (ø)
python	82.37% <ø> (ø)
sqlite	81.71% <ø> (ø)
unit	47.93% <ø> (ø)

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