fix: guard against null metadata in checkCurrentMetadataLocation

[waterWang]

Description

When checkCommitStatus is called during a CREATE TABLE operation (where base == null), refresh() returns null because the table does not yet exist in the metastore. The subsequent call to metadata.metadataFileLocation() throws a NullPointerException, which is swallowed by .suppressFailureWhenFinished(), resulting in a misleading CommitStateUnknownException that tells the user to perform unnecessary manual remediation.

Fix

Add a null check after refresh(). If refresh() returns null, the table does not exist in the catalog, so the commit could not have landed — return false immediately.

Root cause

HiveTableOperations.doRefresh() swallows NoSuchObjectException when currentMetadataLocation() is null (the CREATE TABLE case), leaving currentMetadata == null with shouldRefresh = false. The subsequent refresh() → current() call returns null, which checkCurrentMetadataLocation then dereferences.

Testing

The existing test coverage for checkCommitStatus only covers the update path (table already exists). A CREATE TABLE failure path is not covered by TestHiveCommits. This fix adds a defensive null guard that is trivially correct — the only valid return value when the table metadata is null is false (commit did not land).

Closes #17462

[uros-b]

@waterWang Please note that @superdiaodiao was already working on this in #17464.