tree-wide: introduce mfree()

Pretty trivial helper which wraps free() but returns NULL, so we can
simplify this:
        free(foobar);
        foobar = NULL;
to this:
        foobar = mfree(foobar);

1 files changed, 1 insertions, 2 deletions

diff --git a/src/core/snapshot.c b/src/core/snapshot.c
index 1e634b9bc1..9518e21f36 100644
--- a/src/core/snapshot.c
+++ b/src/core/snapshot.c
@@ -217,8 +217,7 @@ int snapshot_create(Manager *m, const char *name, bool cleanup, sd_bus_error *e,
                                 break;
                         }
 
-                        free(n);
-                        n = NULL;
+                        n = mfree(n);
                 }
         }