remove trailing spaces

Link: https://github.com/GeneAssembly/biosal/issues/448
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
throw error is no memory fence is available

Link: https://github.com/GeneAssembly/biosal/issues/449
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>