Pasting a layer without a checked attribute, appears to be checked in the layer control

[AliyanH]

Example - paste the following layer (note - it does not have a checked attribute) to this experiment

<layer- label="Ottawa">
    <map-meta name="projection" content="OSMTILE"></map-meta>
    <map-meta name="cs" content="gcrs"></map-meta>
    <map-feature>
      <map-featurecaption>Ottawa</map-featurecaption>
      <map-geometry>
        <map-point class="ottawa">
          <map-coordinates>-75.697193 45.421530</map-coordinates>
        </map-point>
      </map-geometry>
      <map-properties>TEST</map-properties>
    </map-feature>
  </layer->

Expected behavior - layer does not get rendered (which is implemented), and the layer is not checked in the layer control (needs to be implemented)

[yhy0217]

Resolved in #887