[BugFix] show create starrocks external table fail

[blanklin030]

Why I'm doing:

What I'm doing:

Fixes #43496

What type of PR is this:

• [x] BugFix
• [ ] Feature
• [ ] Enhancement
• [ ] Refactor
• [ ] UT
• [ ] Doc
• [ ] Tool

Does this PR entail a change in behavior?

• [ ] Yes, this PR will result in a change in behavior.
• [x] No, this PR will not result in a change in behavior.

If yes, please specify the type of change:

• [ ] Interface/UI changes: syntax, type conversion, expression evaluation, display information
• [ ] Parameter changes: default values, similar parameters but with different default values
• [ ] Policy changes: use new policy to replace old one, functionality automatically enabled
• [ ] Feature removed
• [ ] Miscellaneous: upgrade & downgrade compatibility, etc.

Checklist:

• [ ] I have added test cases for my bug fix or my new feature
• [ ] This pr needs user documentation (for new or modified features or behaviors)
  • [ ] I have added documentation for my new feature or new function
• [ ] This is a backport pr

Bugfix cherry-pick branch check:

• [x] I have checked the version labels which the pr will be auto-backported to the target branch
  • [x] 3.3
  • [x] 3.2
  • [x] 3.1
  • [x] 3.0
  • [x] 2.5

[CLAassistant]

All committers have signed the CLA.

[blanklin030]

@DorianZheng I have added unit tests, please help me to check again if there is any problem with my code

[sonarqubecloud[bot]]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[github-actions[bot]]

[FE Incremental Coverage Report]

:white_check_mark: pass : 14 / 17 (82.35%)

file detail

	path	covered_line	new_line	coverage	not_covered_line_detail
:large_blue_circle:	com/starrocks/qe/ShowExecutor.java	3	5	60.00%	[739, 740]
:large_blue_circle:	com/starrocks/sql/common/MetaUtils.java	11	12	91.67%	[295]

[github-actions[bot]]

[BE Incremental Coverage Report]

:white_check_mark: pass : 0 / 0 (0%)