To reproduce

   1. Start the viewer from a terminal, or make the debug console visible after logging in
   2. Open the map e.g. by pressing Ctrl-m or by clicking the Map button (can be made visible from the bottom bar context menu)

  Expected

    * Map opens
    * Debug console or terminal displays

      INFO: openFloater: Opening floater worldmap

      (and no warning)

  Observed

    * Map opens
    * Debug console or terminal displays

      INFO: openFloater: Opening floater worldmap
      WARNING: getChild: Found child named "zoom slider" but of wrong type 12LLSliderCtrl, expecting P8LLSlider


This is due to requesting the child control with the wrong type, which this change fixes.

Merged this fix with e67da2c6e312 and built (linux 64 standalone)
* Warning gone
* Map still works, no perceptible change in behavior noticed.

Not tested: Merging with v-d tip, as I can't build that. (But I know from downloaded test builds that it is affected by this bug.)