generators not working

#### ALL software version info

Software Version Info

```plaintext
python 3.11.9
param 2.2.0
```

#### Description of expected behavior and the observed behavior
should print `g`

#### Complete, minimal, self-contained example code that reproduces the issue

```python
def g():
while True: yield 'g'

import param
class P(param.Parameterized):
p = param.String(allow_refs=True)
p = P(p=g)
#print(next(g()))
print(p.p) # nothing prints
```