Initialization errors when using `cholCsrReal` in `cheb_cov`

[pbeckman]

cheb_cov.c seems to be working with mass lumping, but when I turn off mass lumping I get some cholCsrReal initialization errors. For a minimal example run

./cheb_cov bunny0.obj 1e-4 0 10 32 0

My backtrace is

* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
  * frame #0: 0x0000000100528c50 libbutterfly.dylib`bfCholCsrRealInit(cholCsrReal=0x000000012c804200, mat=0x000000012b6065d0) at chol_csr_real.c:143:24
    frame #1: 0x0000000100003338 cheb_cov`main(argc=7, argv=0x000000016fdfed50) at cheb_cov.c:191:5
    frame #2: 0x000000019d0960e0 dyld`start + 2360

From what I can tell, cholCsrReal->impl is uninitialized (i.e. is NULL). So when we try to write to cholCsrReal->impl->A at src/chol_csr_real.c:143 we have issues.