Cleanup valgrind warnings

Just some minor cleanup to clear up output when running valgrind. A few uninitialised values (one serious), one mismatched new[]/delete.

306992e7064b99b3108fdfc4e0205732dafd2c9b could do with attention from someone who knows how all the "zoom" stuff in SectorView works.

Note that if you do want to use valgrind, then it may be worth putting `#define VALGRIND 1` at the top of contrib/jenkins/lookup3.c. Search for `VALGRIND` in that file to find comments explaining why.