cid#1659758 silence Division or modulo by float zero

Change-Id: I263e8d0e2658bfa4de30c4954101a9126609917e
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/189256
Tested-by: Jenkins
Reviewed-by: David Gilbert <freedesktop@treblig.org>

svgio/source/svgreader/svgrectnode.cxx

@@ -183,6 +183,8 @@ namespace svgio::svgreader
                     frX = frY;
                 }
 
+                assert(fWidth != 0 && fHeight != 0 && "help coverity see it's not zero");
+
                 frX /= fWidth;
                 frY /= fHeight;