TMstate.c: Handle -Wduplicated-branches warnings
Gets rid of these messages from gcc:
TMstate.c: In function ‘GetBranchHead’:
TMstate.c:128:12: warning: this condition has identical branches [-Wduplicated-branches]
if (parseTree->branchHeadTblSize == 0)
^
TMstate.c: In function ‘_XtGetQuarkIndex’:
TMstate.c:183:16: warning: this condition has identical branche [-Wduplicated-branches]
if (parseTree->quarkTblSize == 0)
^