Expect Ink to fail with error when there is no END, but inky fails silently.

Inky version: 0.15.1
ink version: 1.2.0
inkjs version: 2.2.3

Steps to reproduce:

Step 1: Start with this simple start knot
```
-> start
=== start ===
We have started
-> END
```

Step 2: Add a gather
```
-> start
=== start ===
We have started
- -> start
-> END
```

Step 3: Remove the END
```
-> start
=== start ===
We have started
- -> start
```

**Issue**: Somewhere between step 2 and 3, user expects infinite loop warning, but Inky fails silently. Subsequent changes to the Ink yields undefined Inky error state. Seem Inky becomes confused.