fix bug in LabeledGraph.clear()
fix bug in LabeledGraph.clear()

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extra : convert_revision : svn%3A3ed01bd8-26fb-0310-9e4c-ca1a4053419f/networkx/trunk%401072

kernc/networkx,jni/networkx,ghdk/networkx,nathania/networkx,ionanrozenfeld/networkx,sharifulgeo/networkx,sharifulgeo/networkx,kai5263499/networkx,aureooms/networkx,aureooms/networkx,jakevdp/networkx,kai5263499/networkx,RMKD/networkx,JamesClough/networkx,NvanAdrichem/networkx,dmoliveira/networkx,debsankha/networkx,beni55/networkx,dmoliveira/networkx,michaelpacer/networkx,kernc/networkx,harlowja/networkx,SanketDG/networkx,wasade/networkx,debsankha/networkx,RMKD/networkx,yashu-seth/networkx,jfinkels/networkx,RMKD/networkx,jakevdp/networkx,dmoliveira/networkx,ionanrozenfeld/networkx,jtorrents/networkx,bzero/networkx,jni/networkx,blublud/networkx,ghdk/networkx,ghdk/networkx,chrisnatali/networkx,chrisnatali/networkx,dhimmel/networkx,bzero/networkx,kernc/networkx,Sixshaman/networkx,debsankha/networkx,farhaanbukhsh/networkx,chrisnatali/networkx,aureooms/networkx,bzero/networkx,harlowja/networkx,jtorrents/networkx,dhimmel/networkx,farhaanbukhsh/networkx,andnovar/networkx,blublud/networkx,harlowja/networkx,nathania/networkx,jakevdp/networkx,nathania/networkx,kai5263499/networkx,jcurbelo/networkx,dhimmel/networkx,goulu/networkx,sharifulgeo/networkx,cmtm/networkx,blublud/networkx,ltiao/networkx,farhaanbukhsh/networkx,jni/networkx,OrkoHunter/networkx,ionanrozenfeld/networkx,tmilicic/networkx