Don't Set unintialized pointers to 0 or NULL set to nullptr

If you must have a raw pointer that you do not have at construction or definition time
```C++
MyPointedAtClass* my_pointer = nullptr;
```
```C++
MyClass::Myclass() : my_pointer_(nullptr) {}
```

This is a list of these found but that are not yet fixed

- [ ] `SimpleFixedNodeBranch::MyEstimator`

- [ ] `Login in other files based on SimpleFixedNodeBranch::getEstimaterManager()`