Arch: Fix missing cache value for SectionPlane

When the Arch SectionPlane was rendered via TechDraw in Solid mode, the
last parameter "fillSpaces" was not set for the svgcache.
So the next render operation threw an exeption because there where only
4 instead of 5 elements in the cache list.

src/Mod/Arch/ArchSectionPlane.py

@@ -298,7 +298,7 @@ def getSVG(section, renderMode="Wireframe", allOn=False, showHidden=False, scale
                 svgcache += render.getHiddenSVG(linewidth="SVGLINEWIDTH")
             svgcache += '</g>\n'
             # print(render.info())
-            section.Proxy.svgcache = [svgcache,renderMode,showHidden,showFill]
+            section.Proxy.svgcache = [svgcache,renderMode,showHidden,showFill,fillSpaces]
     else:
 
         if not svgcache: