Disable fallback to identity coef matrix in LCAO

**Describe the bug**
@mcbennet hit this issue
```

```
fails because of missing `coefficient` line and if changed to
```

```
everything works as expected.
The reason is when LCAO spo was constructed if no `coefficient` was found, the code treat the MO coefficients matrix as identity. This behavior was used for system with 1 electron for convenience. However it is more likely a user error. For this reason, the code should not fallback and issue an error. If the identity matrix behavior, it should be explicitly requested for example like
```

```