don't merge single checks into a checkgroup

[Klumbumbus]

What steps will reproduce the problem?

1. use this preset code

    <chunk id="highway_yesno">
        <checkgroup columns="2">
            <check key="bridge" text="Bridge" disable_off="true" />
            <check key="tunnel" text="Tunnel" disable_off="true" />
            <check key="embankment" text="Embankment" disable_off="true" />
            <check key="cutting" text="Cutting" disable_off="true" />
        </checkgroup>
    </chunk>
    <chunk id="highway_yesno_oneway">
        <check key="oneway" text="Oneway" />
        <reference ref="highway_yesno" />
    </chunk>
    
        <item name="Test" icon="presets/service/fire_hydrant.svg" type="node" preset_name_label="true">
            <reference ref="highway_yesno_oneway" />
        </item> <!-- Test -->

What is the expected result?

What happens instead?

Please provide any additional information below. Attach a screenshot if possible.

Same problem without chunks too. In fact we currently use a workaround in our internal steps preset. I used the example with chunk as chunks are used several times which makes it easy that this error slips in somewhere without noticing when editing the preset file.

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2019-05-07 22:30:33 +0200 (Tue, 07 May 2019)
Build-Date:2019-05-08 01:30:50
Revision:15060
Relative:URL: ^/trunk

Identification: JOSM/1.5 (15060 en) Windows 10 64-Bit
OS Build number: Windows 10 Pro 1803 (17134)
Memory Usage: 883 MB / 1820 MB (595 MB allocated, but free)
Java version: 1.8.0_211-b12, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Screen: \Display0 1680x1050
Maximum Screen Size: 1680x1050
VM arguments: [-Djava.security.manager, -Djava.security.policy=file:<java.home>\lib\security\javaws.policy, -DtrustProxy=true, -Djnlpx.home=<java.home>\bin, -Djnlpx.origFilenameArg=C:\Program Files (x86)\josm-latest.jnlp, -Djnlpx.remove=false, -Djava.util.Arrays.useLegacyMergeSort=true, -Djnlpx.heapsize=NULL,2048m, -Djnlpx.splashport=61278, -Djnlpx.jvm=<java.home>\bin\javaw.exe]
Dataset consistency test: No problems found

[Don-vip]

what is the workaround we use?

[Klumbumbus]

        <item name="Steps" icon="presets/transport/way/steps.svg" type="way" preset_name_label="true">
            <link wiki="Tag:highway=steps" />
            <key key="highway" value="steps" />
            <optional>
                <reference ref="name_layer" />
                <reference ref="surface" />
                <text key="step_count" text="Amount of Steps" />
                <space />
                <checkgroup columns="1" > <!-- workaround -->
                    <check key="ramp" text="Ramp" />
                </checkgroup>
                <checkgroup columns="2" >
                    <check key="ramp:stroller" text="Stroller ramp" />
                    <check key="ramp:bicycle" text="Bicycle ramp" />
                </checkgroup>
                <combo key="ramp:wheelchair" text="Wheelchair ramp" values="yes,limited,no" />
                <combo key="ramp:luggage" text="Luggage ramp" values="yes,automatic,manual,no" />
                <space />
                <checkgroup columns="1" > <!-- workaround -->
                    <check key="handrail" text="Handrail" />
                </checkgroup>
                <checkgroup columns="3" >
                    <check key="handrail:left" text="Left handrail" />
                    <check key="handrail:center" text="Center handrail" />
                    <check key="handrail:right" text="Right handrail" />
                </checkgroup>
                <space />
                <combo key="conveying" text="Escalator" values="yes,forward,backward,reversible" />
                <space />
                <reference ref="highway_yesno_incline_oneway_lit_width" />
            </optional>
        </item> <!-- Steps -->

[Don-vip]

In 15072/josm:

fix #17698 - don't merge single checks into immediate following checkgroup

[Klumbumbus]

Thanks.