Fontconfig error output due to malformed conf file

Generating new string page texture 121: 256x256, total string texture memory is 393.22 KB
Generating new string page texture 122: 128x256, total string texture memory is 2.79 MB
Fontconfig error: "/etc/fonts/conf.d/10-scale-bitmap-fonts.conf", line 70: non-double matrix element
Fontconfig error: "/etc/fonts/conf.d/10-scale-bitmap-fonts.conf", line 70: non-double matrix element
Fontconfig warning: "/etc/fonts/conf.d/10-scale-bitmap-fonts.conf", line 78: saw unknown, expected number
Generating new string page texture 136: 2048x256, total string texture memory is 4.88 MB
Installing breakpad exception handler for appid(steamwebhelper)/version(20150130171142)
Installing breakpad exception handler for appid(steamwebhelper)/version(1422637902)

Above output is produced, eg by steam when running a game.

The fontconfig error lines can be verified with "fc-cache -v | grep -i err".

The offending section is around original lines 70, 78:

<match target="font">
  <test name="scalable" compare="eq">
    <bool>false</bool>
  </test>
  <test name="pixelsizefixupfactor" compare="not_eq">
    <double>1.0</double>
  </test>
  <edit name="matrix" mode="assign">
    <times>
      <name>matrix</name>
      <matrix>
        <name>pixelsizefixupfactor</name> <double>0</double>
        <double>0</double> <name>pixelsizefixupfactor</name>
       </matrix>
    </times>
  </edit>
  <edit name="size" mode="assign">
    <divide>
      <name>size</name>
      <name>pixelsizefixupfactor</name>
    </divide>
  </edit>
</match>

Note that the <matrix> element has 2 <name> child elements when it should only have 1. Removal of the second "<name>pixelsizefixupfactor</name>" solves the error. After this removal neither fc-cache nor steam report an "Fontconfig error:".

The documentation for fonts.conf, eg http://linux.die.net/man/5/fonts-conf, suggests that the <matrix> element should hold 4 <double> elements:

><MATRIX>
>
>This element holds the four <double> elements of an affine transformation.

But it appears not to produce an error when only 2 elements are present (and does produce an error here when there are 4, for me).

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: fontconfig-config 2.11.1-0ubuntu3
ProcVersionSignature: Ubuntu 3.16.0-29.39-generic 3.16.7-ckt2
Uname: Linux 3.16.0-29-generic x86_64
ApportVersion: 2.14.7-0ubuntu8.1
Architecture: amd64
CurrentDesktop: KDE
Date: Sun Feb 1 00:46:10 2015
InstallationDate: Installed on 2012-11-02 (820 days ago)
InstallationMedia: Kubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.1)
PackageArchitecture: all
SourcePackage: fontconfig
UpgradeStatus: Upgraded to utopic on 2015-01-28 (3 days ago)
modified.conffile..etc.fonts.conf.avail.10.scale.bitmap.fonts.conf: [modified]
mtime.conffile..etc.fonts.conf.avail.10.scale.bitmap.fonts.conf: 2015-02-01T00:30:44.308962