fix(visualization): define the render_error the table charts already call

common/workflow-operator/src/main/scala/org/apache/texera/amber/operator/visualization/figureFactoryTable/FigureFactoryTableOpDesc.scala

@@ -104,6 +104,9 @@ class FigureFactoryTableOpDesc extends PythonOperatorDescriptor {
        |
        |class TableChartOperator(UDFTableOperator):
        |
+       |    def render_error(self, error_msg) -> str:
+       |        return f"<h1>Figure Factory Table is not available.</h1><p>Reason is: {error_msg}</p>"
+       |
        |    def process_table(self, table: Table, port: int) -> Iterator[Optional[TableLike]]:
        |
        |        if table.empty:

common/workflow-operator/src/main/scala/org/apache/texera/amber/operator/visualization/tablesChart/TablesPlotOpDesc.scala

@@ -76,6 +76,9 @@ class TablesPlotOpDesc extends PythonOperatorDescriptor {
        |import plotly.io
        |class TableChartOperator(UDFTableOperator):
        |
+       |    def render_error(self, error_msg) -> str:
+       |        return f"<h1>Tables Plot is not available.</h1><p>Reason is: {error_msg}</p>"
+       |
        |    def process_table(self, table: Table, port: int) -> Iterator[Optional[TableLike]]:
        |
        |        if table.empty:

common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/visualization/figureFactoryTable/FigureFactoryTableOpDescSpec.scala

@@ -99,4 +99,15 @@ class FigureFactoryTableOpDescSpec extends AnyFlatSpec with BeforeAndAfter with
     assert(carries(code, "col_two"))
     code should include("class TableChartOperator(UDFTableOperator)")
   }
+
+  it should "define the render_error the empty-table branches call" in {
+    // Both empty-table branches call self.render_error; without the definition they
+    // raised AttributeError instead of rendering the message.
+    withColumns()
+    val code = opDesc.generatePythonCode()
+    code should include("def render_error(self, error_msg) -> str:")
+    code should include(
+      """return f"<h1>Figure Factory Table is not available.</h1><p>Reason is: {error_msg}</p>""""
+    )
+  }
 }

common/workflow-operator/src/test/scala/org/apache/texera/amber/operator/visualization/tablesChart/TablesPlotOpDescSpec.scala

@@ -88,4 +88,15 @@ class TablesPlotOpDescSpec extends AnyFlatSpec with BeforeAndAfter with Matchers
     )
     code should not include "')','"
   }
+
+  it should "define the render_error the empty-table branches call" in {
+    // Both empty-table branches call self.render_error; without the definition they
+    // raised AttributeError instead of rendering the message.
+    opDesc.includedColumns = List(column("col_one"), column("col_two"))
+    val code = opDesc.generatePythonCode()
+    code should include("def render_error(self, error_msg) -> str:")
+    code should include(
+      """return f"<h1>Tables Plot is not available.</h1><p>Reason is: {error_msg}</p>""""
+    )
+  }
 }