split_grid broken with Wilson Clover when QUDA_CLOVER_RECONSTRUCT=ON

[chaoos]

When using the split_grid with the Wilson Clover operator and QUDA_CLOVER_RECONSTRUCT=ON, splitting the Clover field leads to an error:

QUDA (rank=0): ERROR: 0x556253f17210 diagonal appears unset (rank 0, host geno, clover_field_order.h:646 in quda::clover::FloatNOrder<Float, length, N, add_rho, enable_reconstruct_, huge_alloc>::FloatNOrder(const quda::CloverField&, bool, Float*) [with Float = double; int length = 72; int N = 2; bool add_rho = false; bool enable_reconstruct_ = true; bool huge_alloc = false]())
QUDA (rank=0):        last kernel called was (name=cudaMemcpyDefault,volume=bytes=37158912,aux=copy_from_buffer,clover_field.cpp,343)

I was able to track down where it appears. In the instantiation of the order class of the collected clover field for the split_grid in https://github.com/lattice/quda/blob/develop/lib/copy_clover_offset.cu#L19C1-L19C38. The reason is that at that point the collected clover field (out) is not initialized with values yet, thus the diagonals are indeed zero.

[maddyscientist]

Thanks @chaoos for the bug report. My first thought was how did that slip through the net, with out CI, but I see now that we idon'thave split grid clover enabled in the CI. I guess we will need to get that fixed.