Assert running_iseq before using it

When running_iseq happens to be 0, it's better to fail on the assertion
rather than referencing the null pointer.

1 files changed, 2 insertions, 2 deletions

diff --git a/yjit/src/core.rs b/yjit/src/core.rs
index 3843e91e2e..90e6490997 100644
--- a/yjit/src/core.rs
+++ b/yjit/src/core.rs
@@ -2749,14 +2749,14 @@ fn branch_stub_hit_body(branch_ptr: *const c_void, target_idx: u32, ec: EcPtr) -
         let original_interp_sp = get_cfp_sp(cfp);
 
         let running_iseq = get_cfp_iseq(cfp);
+        assert_eq!(running_iseq, target_blockid.iseq as _, "each stub expects a particular iseq");
+
         let reconned_pc = rb_iseq_pc_at_idx(running_iseq, target_blockid.idx.into());
         let reconned_sp = original_interp_sp.offset(target_ctx.sp_offset.into());
         // Unlike in the interpreter, our `leave` doesn't write to the caller's
         // SP -- we do it in the returned-to code. Account for this difference.
         let reconned_sp = reconned_sp.add(target_ctx.is_return_landing().into());
 
-        assert_eq!(running_iseq, target_blockid.iseq as _, "each stub expects a particular iseq");
-
         // Update the PC in the current CFP, because it may be out of sync in JITted code
         rb_set_cfp_pc(cfp, reconned_pc);