8221456: nmethod::make_unloaded() clears _method member too early

Reviewed-by: eosterlund, thartmann

src/hotspot/share/code/nmethod.cpp

@@ -1089,7 +1089,6 @@ void nmethod::make_unloaded() {
     if (_method->code() == this) {
       _method->clear_code(); // Break a cycle
     }
-    _method = NULL;            // Clear the method of this dead nmethod
   }
 
   // Make the class unloaded - i.e., change state and notify sweeper
@@ -1109,6 +1108,9 @@ void nmethod::make_unloaded() {
     Universe::heap()->unregister_nmethod(this);
   }
 
+  // Clear the method of this dead nmethod
+  set_method(NULL);
+
   // Log the unloading.
   log_state_change();