Fix use after free and calls to operator comma in debug mode

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@232703 91177308-0d34-0410-b5e6-96231b3b80d8

src/debug.cpp

@@ -214,10 +214,10 @@ __libcpp_db::__erase_i(void* __i)
             else
                 q->__next_ = p->__next_;
             __c_node* c = p->__c_;
-            free(p);
             --__isz_;
             if (c != nullptr)
                 c->__remove(p);
+            free(p);
         }
     }
 }