Fix a memory leak in lalg_exp used in the Lanczos propagator.

8 jobs for fix_memory_leak in 0 seconds
Status Job ID Name Coverage
  External
failed Octopus Buildbot

11:10:00

passed codecov/patch

100.0%
passed codecov/project

68.28135%
passed codecov/project

66.09573%
passed codecov/project

67.59391%
passed codecov/project

66.1046%
passed codecov/project

66.03436%
passed codecov/project

68.22023%