EAMxx: bug in fieldwithininternal check

this type of logic

```cpp
          if (v(i)<result.min_val) {
            result.min_val = v(i);
            result.min_loc = i;
          }
          if (v(i)>result.max_val) {
            result.max_val = v(i);
            result.max_loc = i;
          }
```

doesn't capture a column full of nans


fix incoming ... 🤕 