RELIABILITY: Fix memory leaks and dereferences of uninitialized pointers.

The 'total' struct and 'm' array in struct reliability were allocated once
per case group, but freed exactly once.  If there were no case groups,
this caused a null dereference.  If there was more than one case group,
this caused a memory leak.  This commit fixes both problems.

This commit also fixes a related crash on bad syntax due to dereferencing
a null pointer in reliability_destroy().

Bug #38660.
Reported by William Rogers.