The return type of H5A_create was changed from hid_t to H5A_t *
but the test was not changed (still doing H5A_create(...) < 0).
Fixed the error by changing to compare against NULL.

Tested: ADA AIX machine where the old code was flagged as an error by the AIX compiler.


git-svn-id: https://svn.hdfgroup.uiuc.edu/hdf5/trunk@25721 dab4d1a6-ed17-0410-a064-d1ae371a2980