Avoid calling `mrb_env_unshare()` when `env` is `NULL`.

Small performance improvement by reducing function invocations.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/vm.c b/src/vm.c
index 06431b2f0..57df10ace 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -300,7 +300,7 @@ cipop(mrb_state *mrb)
   struct REnv *env = c->ci->env;
 
   c->ci--;
-  mrb_env_unshare(mrb, env);
+  if (env) mrb_env_unshare(mrb, env);
 }
 
 void mrb_exc_set(mrb_state *mrb, mrb_value exc);