Vector: Fix operator[]

Istg Vector has a curse or something, the annoying and inexplicable bugs always end up in Vector.

libluna/include/luna/Vector.h

@@ -106,13 +106,13 @@ template <typename T> class Vector
     const T& operator[](usize index) const
     {
         check(index < m_size);
-        return m_data[m_size];
+        return m_data[index];
     }
 
     T& operator[](usize index)
     {
         check(index < m_size);
-        return m_data[m_size];
+        return m_data[index];
     }
 
     Iterator begin()