[FIXED] [#1598] [4.7.0] Button not enabled after combobox has used Forceselection

[Selas]

<form id="form1" runat="server">
        <ext:ResourceManager runat="server" />
        <ext:FormPanel runat="server" Width="500" DefaultButton="btnSave">
            <Items>
                <ext:TextField
                    runat="server"
                    AllowBlank="false"
                    FieldLabel="fieldlabel"
                    LabelWidth="130"
                    AnchorHorizontal="100%"
                    MaskRe="/[^<>]/">
                </ext:TextField>
                <ext:ComboBox
                    runat="server"
                    FieldLabel="fieldlabel"
                    AllowBlank="false"
                    LabelWidth="130"
                    AnchorHorizontal="100%"
                    TypeAhead="true"
                    ForceSelection="true">
                    <Items>
                        <ext:ListItem Text="BBBB" Value="1" />
                        <ext:ListItem Text="CCCC" Value="2" />
                        <ext:ListItem Text="DDDD" Value="3" />
                    </Items>
                </ext:ComboBox>
            </Items>
            <Buttons>
                <ext:Button ID="btnSave" runat="server" Text="Save" FormBind="true" />
                <ext:Button ID="btnCancel" runat="server" Text="Cancel" />
            </Buttons>
        </ext:FormPanel>

    </form>

In the Form, I fill in "a" in the textField and TAB, then fill in "a" in the combobox and TAB. ForceSelection clears the combobox. All normal but when I then choose a valid value for the combobox, it is not revalidated again and my saveButton stays disabled?