Fixed listSchemas to return empty result set in case of empty string catalog (#1131)

## Description
<!-- Provide a brief summary of the changes made and the issue they aim
to address.-->
Fixed listSchemas to return empty result set in case of empty string
catalog
## Testing
<!-- Describe how the changes have been tested-->
Added a test for the fix
## Additional Notes to the Reviewer
<!-- Share any additional context or insights that may help the reviewer
understand the changes better. This could include challenges faced,
limitations, or compromises made during the development process.
Also, mention any areas of the code that you would like the reviewer to
focus on specifically. -->
Fixes
[PECOBLR-1371](https://databricks.atlassian.net/browse/PECOBLR-1371)

NO_CHANGELOG=true
[PECOBLR-1371]:
https://databricks.atlassian.net/browse/PECOBLR-1371?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

Author: msrathore-db

src/main/java/com/databricks/jdbc/dbclient/impl/sqlexec/DatabricksMetadataSdkClient.java

@@ -71,6 +71,17 @@ public DatabricksResultSet listCatalogs(IDatabricksSession session) throws SQLEx
   public DatabricksResultSet listSchemas(
       IDatabricksSession session, String catalog, String schemaNamePattern) throws SQLException {
     catalog = autoFillCatalog(catalog, session);
+
+    // Return empty result set if catalog is an empty string
+    if (catalog != null && catalog.isEmpty()) {
+      LOGGER.debug("Catalog is empty string, returning empty result set for listSchemas");
+      return metadataResultSetBuilder.getResultSetWithGivenRowsAndColumns(
+          SCHEMA_COLUMNS,
+          new ArrayList<>(),
+          METADATA_STATEMENT_ID,
+          com.databricks.jdbc.common.CommandName.LIST_SCHEMAS);
+    }
+
     CommandBuilder commandBuilder =
         new CommandBuilder(catalog, session).setSchemaPattern(schemaNamePattern);
     String SQL = commandBuilder.getSQLString(CommandName.LIST_SCHEMAS);

src/test/java/com/databricks/jdbc/dbclient/impl/sqlexec/DatabricksMetadataSdkClientTest.java

@@ -1085,4 +1085,25 @@ void testListCrossReferences_handlesNullSqlStateWithoutNPE() throws Exception {
                 TEST_SCHEMA,
                 TEST_TABLE));
   }
+
+  @Test
+  void testListSchemasWithEmptyCatalog() throws SQLException {
+    IDatabricksConnectionContext mockContext = mock(IDatabricksConnectionContext.class);
+    when(mockContext.getEnableMultipleCatalogSupport()).thenReturn(false);
+    when(session.getCurrentCatalog()).thenReturn("");
+    when(mockClient.getConnectionContext()).thenReturn(mockContext);
+
+    DatabricksMetadataSdkClient metadataClient = new DatabricksMetadataSdkClient(mockClient);
+
+    // Call listSchemas with empty catalog
+    DatabricksResultSet actualResult = metadataClient.listSchemas(session, "", null);
+
+    // Verify the result set is empty
+    assertNotNull(actualResult);
+    assertEquals(StatementState.SUCCEEDED, actualResult.getStatementStatus().getState());
+    assertEquals(METADATA_STATEMENT_ID, actualResult.getStatementId());
+    assertEquals(0, ((DatabricksResultSetMetaData) actualResult.getMetaData()).getTotalRows());
+    assertFalse(
+        actualResult.next(), "Expected empty result set for listSchemas with empty catalog");
+  }
 }