Fix error reported by Valgrind

Fix this error:
 ==6514== Mismatched free() / delete / delete []
reported by valgrind. This is a minimal fix for the
reported problem.

Note there are some other strange looking things in the file
that I did not fix.  The following line appears to mistakenly
use ">" instead of "<"
    if (matchedCand.pt() > ptBins.at(0)) { // underflow problem

This fix is for 7_0_X and 7_1_X. There are similar
problems in 6_2_X which someone might want to fix if this
is used in 6_2_X, although the code has been modified since
then so the exact same fix will not work.
Merge pull request #2299 from wddgit/fix70XMatchCandidateBenchmark

DQM fixes -- Fix error reported by Valgrind in DQMOffline/PFTau