The createOsqpSparseMatrix does not correctly handle empty sparse matrix.

When setting the hessian which has zero nonZero entries it creates an osqp hessian with one value initialized to garbage.

Current:
```
OSQP Hessian:
nzmax:1
m:19
n:19
p:0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
i:93825007825568
x:4.64e-310
```

Expected:
```
OSQP Hessian:
nzmax:0
m:19
n:19
p:0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
i:
x:
```

Start at createOsqpSparseMatrix, the entry point named in the issue, and trace how a zero-nonzero Eigen sparse matrix is converted to OSQP storage. Reproduce the 19x19 empty Hessian case and add or update a regression test if the repository has coverage for this conversion. Done means the resulting OSQP Hessian has nzmax 0 with empty i and x arrays.

Written by the indexing model from the issue text.