Corrected default size value for update buffer hooks

[Izueh]

Was having issues in an addon for FFXV when hooking to this event, was consistently getting size 0 for all update buffer calls. this seems to be a bug.

from DX11 docs: https://learn.microsoft.com/en-us/windows/win32/api/d3d11/nf-d3d11-id3d11devicecontext-updatesubresource

[in, optional] pDstBox
Type: const D3D11_BOX*
A pointer to a box that defines the portion of the destination subresource to copy the resource data into. Coordinates are in bytes for buffers and in texels for textures. If NULL, the data is written to the destination subresource with no offset. The dimensions of the source must fit the destination (see D3D11_BOX).

seems to me like it's saying it should fill the destination when pDstBox is null so it should default to the buffer size and not SrcRowPitch.