Null Pointer (possible bug?) On ListGrid with AlwaysShowEditors = true

[chimpeenuts]

Issue description:

Am attempting to invalidate and re-fresh a SQL-based datasource-fed ListGrid with setAlwaysShowEditors = true.

Upon refresh, null pointer exception appears in client output. Issue does *not* occur when setAlwaysShowEditors = false.

In digging through the javascript, it appears there is either (a) a race condition between fetching data and redrawing the grid OR (b) a missing NULL check to prevent issue from occurring.

1. v8.3p_2013-02-24/PowerEdition Deployment (built 2013-02-24)

Although checked SmartClient v9.1 nightlies and same javascript code appears.

2. Firefox (version 26.0) and Chrome (latest version).

5. Stack trace:

ERROR: 15:19:00.877:TMR8:WARN:Log:TypeError: Cannot read property 'getItems' of null
Stack from error.stack:
    ListGrid._clearingInactiveEditorHTML() @ SNAP/sc/modules/ISC_Grids.js:1092:343
    GridBody.redraw() @ SNAP/sc/modules/ISC_Grids.js:607:48
    [c]Canvas.clearRedrawQueue() @ SNAP/sc/modules/ISC_Core.js:2222:110
    [c]Class.fireCallback() @ SNAP/sc/modules/ISC_Core.js:257:78
    Timer._fireTimeout() @ SNAP/sc/modules/ISC_Core.js:943:81
    <anonymous>:1:11() @ 

com.smartgwt.client.core.JsObject$SGWT_WARN: 15:19:00.877:TMR8:WARN:Log:TypeError: Cannot read property 'getItems' of null
Stack from error.stack:
    ListGrid._clearingInactiveEditorHTML() @ SNAP/sc/modules/ISC_Grids.js:1092:343
    GridBody.redraw() @ SNAP/sc/modules/ISC_Grids.js:607:48
    [c]Canvas.clearRedrawQueue() @ SNAP/sc/modules/ISC_Core.js:2222:110
    [c]Class.fireCallback() @ SNAP/sc/modules/ISC_Core.js:257:78
    Timer._fireTimeout() @ SNAP/sc/modules/ISC_Core.js:943:81
    <anonymous>:1:11() @ 

	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
	at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:105)
	at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
	at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
	at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:293)
	at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:547)
	at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:364)
	at java.lang.Thread.run(Thread.java:744)

Here is javascript source code (ISC_Grids.js) where the issue occurs:

isc.A.$69l = function isc_ListGrid__clearingInactiveEditorHTML(_1, _2) {
        if (this.$69m == null)return;
        if (!this.$286 || !this.$686((_2 != null ? this.getField(_2) : null), true))return;
        if (_1 != null) {
            var _3 = "_" + _1 + "_" + _2, _4 = this.$69m[_3];
            if (_4) {
                _4.formItem.clearInactiveEditorContext(_4);
                delete this.$69m[_3]
            }
        } else {
            var _5 = this.getEditForm(), _6 = _5.getItems();
            for (var i = 0; i < _6.length; i++) {
                _6[i].clearAllInactiveEditorContexts()
            }
            delete this.$69m
        }

As you can see there is no NULL check on _5 before it is accessed. In my browser debugging, when using breakpoints, getEditForm() was returning NULL but very soon after was actually returning a non-null value. What I think may be happening is that when the list grid is cleared (or invalidated) the editForm is cleared or becomes null...however once the data arrives, the editForm is re-initialized.

6. Code used to generate error

1) Create a ListGrid and a button
2) Set the ListGrid to use a SQL-based datasource
3) Setup the button so when clicked it calls a cancelEditing, invalidate, and fetchData
4) Press button. Then press button again. Observe error. Each time button is pressed, error occurs.

Here is source code to generate example:
DataSource file

<DataSource ID="task" serverType="sql" tableName="collection_task" dropExtraFields="true">
<fields>
    <field name="id" type="sequence" hidden="true" primaryKey="true"/>
    <field name="interface_id" type="integer" />
</fields>

</DataSource>

SmartGWT Java code:

public class TestGrid extends VLayout {
private ListGridField _interfaceField;
protected ToolStrip _toolStrip;

public TestGrid() {
_interfacesGrid = new ListGrid();
		_interfacesGrid.setDataSource(DataSource.get("task"));
_interfacesGrid.setWidth100();
_interfacesGrid.setHeight100();
_interfacesGrid.setAlwaysShowEditors(true);
_interfacesGrid.setAutoSaveEdits(false);

_toolStrip = new ToolStrip();
ToolStripButton button = new ToolStripButton("Apply Settings...");
button.addClickHandler(new ClickHandler() {
  public void onClick(ClickEvent event) {
   refreshDataFromServer();
 }
});

_toolStrip.addButton(button);
_toolStrip.addFill();
_toolStrip.setWidth100();

addMember(_toolStrip);

addMember(_interfacesGrid);
}

private void refreshDataFromServer() {
  _interfacesGrid.discardAllEdits();
  _interfacesGrid.invalidateCache();
  _interfacesGrid.fetchData();
}

}