Missing DSLD code assist proposals at start of non-empty closure block for delegate type

Consider the following:

some.dsld:
```groovy
contribute(isScript() & enclosingCallName('foo') & inClosure() & isThisType()) {
  setDelegateType(String)
}
```
script.groovy:
```groovy
foo {
  |
  whatever
}
```

Content assist (Ctrl+Space) at `|` is missing proposals for the DSLD-supplied delegate type (`java.lang.String` in this case).