Bug: Line highlighting does not work for XML file

[KamalnathOSU]

I used the following XML segment in a slide and wanted to highlight lines 3,9,7 (in that order) but it does not work. I think it is a bug.

```xml {all|3|9|7}
   <Alloy name="Mo_alloy">
    <primary_phase name="Bcc" />
    <solvent name="Mo" />
    <ParameterTable name="kinetic" type="kinetic">
      <Parameter name="interfacial_energy" value="0.4" description="Interfacial energy [J/m^2]." />      
      <Parameter name="solute_trapping_parameter" value="4e-9" description="Solute trapping parameter." />
      <Parameter name="solute_drag_parameter" value="0.1" description="Between 0 and 1; Solute drag parameter." />
      <Parameter name="coarsening_geometric_factor" value="1.5" description="A factor adjusting the coarsening speed of the dendrite." />
	  <Parameter name="coordinate" value="1" description="Describe the geometry of dendrite for back diffusion model: 0 for plate; 1 for cylinder; 2 for sphere" />
      <Parameter name="latent_heat" value="5.5e9" description="Latent Heat of the alloy [J/m^3]." />
      <Parameter name="sound_velocity" value="1000" description="Sound velocity [m/s]." />
      <Parameter name="dendrite_tip_factor" value="1.5" description="Dendrite tip factor. Default value is 1." />
      <Parameter name="solid_diffusivity_factor" value="1" description="A factor adjusting the diffusivity of the solid phase. Default value is 1." />
      <Parameter name="boundary_layer_factor" value="1" description="A factor adjusting the boundary layer. Default value is 1." />
    </ParameterTable>
  </Alloy>