systemc: Add some additional error checks.

Change-Id: I19c5e6f1795c2777dbe7d210cfa01f6ced2020f3
Reviewed-on: https://gem5-review.googlesource.com/c/12815
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
4 files changed