get rid of clang errors

TODO

@@ -23,6 +23,7 @@
 * cleanup - see https://github.com/skypjack/entt/commit/ad5cedc08c83e8cbcc8aaeac9634d44624ffe35a#commitcomment-32380903
 
 ==> can we do more for shared libraries? who knows... see #144
+* get rid of get_pool_data (welcome structured bindings)
 * to be updated: dispatcher
 * to be updated: registry
 * to be updated: emitter

src/entt/entity/registry.hpp

@@ -76,8 +76,8 @@ class registry {
         }
 
         void destroy_if(registry &, const Entity entity) {
-            if(has(entity)) {
-                destroy(entity);
+            if(this->has(entity)) {
+                this->destroy(entity);
             }
         }
     };