Colormap is not saved in layout xml

[christophfroehlich]

Despite ce07e1b and the activated checkbox

the colormap is not saved in the layout xml. hence, after a clean environment (docker rebuild for example), the map is missing.

in some plot used:

      <plot background_colormap="lightcoral" style="Lines" mode="TimeSeries" flip_x="false" flip_y="false" background_data="pump_limited">

but the section is missing in the xml:

 <previouslyLoaded_Streamer name="ROS2 Topic Subscriber"/>
 <!-- - - - - - - - - - - - - - - -->
 <customMathEquations>
  <snippet name="pump_limited">
   ...
  </snippet>
 </customMathEquations>
 <snippets/>
 <!-- - - - - - - - - - - - - - - -->
</root>

Ubuntu 24.04, plotjuggler 3.10.11 installed from ros-humble-plotjuggler-ros

$ apt show ros-humble-plotjuggler
Package: ros-humble-plotjuggler
Version: 3.10.11-1jammy.20250727.225740