fix(document_extractor): xlsx file column int type error (#21408)

api/core/workflow/nodes/document_extractor/node.py

                 df = df.applymap(lambda x: " ".join(str(x).splitlines()) if isinstance(x, str) else x)  # type: ignore
 
                 # Combine multi-line text in column names into a single line
-                df.columns = pd.Index([" ".join(col.splitlines()) for col in df.columns])
+                df.columns = pd.Index([" ".join(str(col).splitlines()) for col in df.columns])
 
                 # Manually construct the Markdown table
                 markdown_table += _construct_markdown_table(df) + "\n\n"

api/tests/unit_tests/core/workflow/nodes/test_document_extractor_node.py

     assert result == ""
 
     assert mock_excel_instance.parse.call_count == 2
+
+
+@patch("pandas.ExcelFile")
+def test_extract_text_from_excel_numeric_type_column(mock_excel_file):
+    """Test extracting text from Excel file with numeric column names."""
+
+    # Test numeric type column
+    data = {1: ["Test"], 1.1: ["Test"]}
+
+    df = pd.DataFrame(data)
+
+    # Mock ExcelFile
+    mock_excel_instance = Mock()
+    mock_excel_instance.sheet_names = ["Sheet1"]
+    mock_excel_instance.parse.return_value = df
+    mock_excel_file.return_value = mock_excel_instance
+
+    file_content = b"fake_excel_content"
+    result = _extract_text_from_excel(file_content)
+
+    expected_manual = "| 1.0 | 1.1 |\n| --- | --- |\n| Test | Test |\n\n"
+
+    assert expected_manual == result