Don't use zero as null pointer constant (-Wzero-as-null-pointer-constant)

src/support/allocators/secure.h

@@ -37,7 +37,7 @@ struct secure_allocator : public std::allocator<T> {
         typedef secure_allocator<_Other> other;
     };
 
-    T* allocate(std::size_t n, const void* hint = 0)
+    T* allocate(std::size_t n, const void* hint = nullptr)
     {
         T* allocation = static_cast<T*>(LockedPoolManager::Instance().alloc(sizeof(T) * n));
         if (!allocation) {