Bugfix for GE1/1 geometry customization

I noticed that when I tried to run 
<PRE>
cmsDriver.py SingleMuPt100_cfi -s GEN,SIM --conditions auto:upgradePLS3 --magField 38T_PostLS1 --datatier GEN-SIM --geometry Extended2023Muon --customise Geometry/GEMGeometry/gemGeometryCustoms.custom_GE11_9and10partitions_v1 --eventcontent FEVTDEBUG -n 10 --fileout out_sim.root
</PRE>

on a fresh SLHC9 checkout I got this bug

<PRE>
We have determined that this is simulation (if not, rerun cmsDriver.py with --data)
Step: GEN Spec:
Loading generator fragment from Configuration.Generator.SingleMuPt100_cfi
Step: SIM Spec:
Step: ENDJOB Spec:
globaltag = DES23_62_V1::All
customising the process with custom_GE11_9and10partitions_v1 from Geometry/GEMGeometry/gemGeometryCustoms
Starting  cmsRun  SingleMuPt100_cfi_GEN_SIM.py
globaltag = DES23_62_V1::All
271 DQMStore::DQMStore
HcalTopologyIdealEP::HcalTopologyIdealEP
%MSG-e Specific:  OscarProducer:g4SimHits@beginRun 14-Mar-2014 23:44:58 CET  Run: 1
Could not process q-name of a DDLogicalPart, reason:
No regex-match for namespace=  name=GEMBox11

SpecPar selection is:
//GEMBox11

%MSG
%
</PRE>

This PR fixes that problem. The other geometry customizations keep working though.