SimpleTable issue

Hi,

simpletable is not working to me, maybe I'm doing something wrong.

Getting following error:
TypeError: Failed to execute 'appendChild' on 'Node': parameter 1 is not of type 'Node'.
at org.apache.royale.jewel.supportClasses.table.TableHeaderCell.org.apache.royale.core.UIBase.addElement (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/core/UIBase.js:413:17)
at org.apache.royale.jewel.supportClasses.table.TableHeaderCell.org.apache.royale.core.GroupBase.addElement (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/core/GroupBase.js:165:60)
at Function.org.apache.royale.utils.MXMLDataInterpreter.initializeStrandBasedObject (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/utils/MXMLDataInterpreter.js:236:13)
at Function.org.apache.royale.utils.MXMLDataInterpreter.generateMXMLArray (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/utils/MXMLDataInterpreter.js:125:54)
at Function.org.apache.royale.utils.MXMLDataInterpreter.generateMXMLInstances (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/utils/MXMLDataInterpreter.js:266:50)
at org.apache.royale.jewel.supportClasses.table.TableHeaderCell.org.apache.royale.html.Group.addedToParent (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/html/Group.js:76:50)
at org.apache.royale.jewel.supportClasses.table.TableRow.org.apache.royale.core.UIBase.addElement (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/core/UIBase.js:414:6)
at org.apache.royale.jewel.supportClasses.table.TableRow.org.apache.royale.core.GroupBase.addElement (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/core/GroupBase.js:165:60)
at Function.org.apache.royale.utils.MXMLDataInterpreter.initializeStrandBasedObject (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/utils/MXMLDataInterpreter.js:236:13)
at Function.org.apache.royale.utils.MXMLDataInterpreter.generateMXMLArray (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/utils/MXMLDataInterpreter.js:125:54)
TypeError: Failed to execute 'appendChild' on 'Node': parameter 1 is not of type 'Node'.
at org.apache.royale.jewel.supportClasses.table.TableHeaderCell.org.apache.royale.core.UIBase.addElement (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/core/UIBase.js:413:17)
at org.apache.royale.jewel.supportClasses.table.TableHeaderCell.org.apache.royale.core.GroupBase.addElement (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/core/GroupBase.js:165:60)
at Function.org.apache.royale.utils.MXMLDataInterpreter.initializeStrandBasedObject (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/utils/MXMLDataInterpreter.js:236:13)
at Function.org.apache.royale.utils.MXMLDataInterpreter.generateMXMLArray (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/utils/MXMLDataInterpreter.js:125:54)
at Function.org.apache.royale.utils.MXMLDataInterpreter.generateMXMLInstances (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/utils/MXMLDataInterpreter.js:266:50)
at org.apache.royale.jewel.supportClasses.table.TableHeaderCell.org.apache.royale.html.Group.addedToParent (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/html/Group.js:76:50)
at org.apache.royale.jewel.supportClasses.table.TableRow.org.apache.royale.core.UIBase.addElement (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/core/UIBase.js:414:6)
at org.apache.royale.jewel.supportClasses.table.TableRow.org.apache.royale.core.GroupBase.addElement (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/core/GroupBase.js:165:60)
at Function.org.apache.royale.utils.MXMLDataInterpreter.initializeStrandBasedObject (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/utils/MXMLDataInterpreter.js:236:13)
at Function.org.apache.royale.utils.MXMLDataInterpreter.generateMXMLArray (/Users/luwi/VisualStudioCodeProjects/myFirstRoyale/bin/js-debug/org/apache/royale/utils/MXMLDataInterpreter.js:125:54)

Start with the SimpleTable MXML example and reproduce the error using the stack-trace entry points in TableHeaderCell, TableRow, UIBase.js, GroupBase.js, and MXMLDataInterpreter.js. Trace the header-cell initialization and verify that the table renders without the appendChild TypeError; no test file is mentioned in the issue.

Written by the indexing model from the issue text.