Avoiding line break between RawBlocks

I have a Pandoc filter written in Lua that converts certain Divs into RawBlocks. My problem is that Pandoc seems to insert a newline between these RawBlocks in the LaTeX output, which messes with the layout since newlines between subfigures are significant.

As far as I can see, my filter doesn’t make any newlines:

if FORMAT ~= 'latex' then
  return {}
end

function Div(elem)
   if elem.classes:includes("subtikz") then
      return { pandoc.RawBlock('latex', '\begin{subfigure}'),
               elem,
               pandoc.RawBlock('latex', '\end{subfigure}') }
   end
   
   if elem.classes:includes("figure") then
      return { pandoc.RawBlock('latex', '\begin{figure}'),
               elem,
               pandoc.RawBlock('latex', '\end{figure}') }
   end
   
   return nil
end

And yet, with a simple Markdown input file, we can see the problem:

<div class="figure">
 hspace{-2cm}
 <div class="subtikz"></div>
 <div class="subtikz"></div>
 
 vspace{8ex}
 
 <div class="subtikz"></div>
</div>

(this is of course heavily simplified — in my real use case I can have content inside the <div class="subtikz">, which is why it’s a div).

This results in:

$ pandoc --lua-filter latex-output-space.lua latex-output-space.md  -t latex
begin{figure}

hspace{-2cm}

begin{subfigure}

end{subfigure}

begin{subfigure}

end{subfigure}

vspace{8ex}

begin{subfigure}

end{subfigure}

end{figure}

Note the extra lines after the end{subfigure} lines. How do I get rid of them? My intended output would be:

begin{figure}
hspace{-2cm}
begin{subfigure}
end{subfigure}
begin{subfigure}
end{subfigure}

vspace{8ex}

begin{subfigure}
end{subfigure}
end{figure}