Emit stackmaps even in unoptimized code if slow path pushes untagged values.

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 569ae50404708ac039e72c5463025beb2d3e265c..7914cef2a37c497196035736f71c1a999aaac25e 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -12662,8 +12662,7 @@ RawStackmap* Code::GetStackmap(
       return map->raw();  // We found a stack map for this frame.
     }
   }
-  // If the code has stackmaps, it must have them for all safepoints.
-  UNREACHABLE();
+  ASSERT(!is_optimized());
   return Stackmap::null();
 }