MetaFieldRanker ignores missing_meta="drop" when meta values can't be sorted #13230

Describe the bug
MetaFieldRanker with missing_meta="drop" still returns documents that don't have the meta field, if the other documents have values that can't be sorted together.

Error message
No error. The ranker logs these warnings and then returns the document anyway:

... the Documents with IDs 3 don't have this meta key.
Because the parameter <missing_meta> is set to 'drop', these Documents will be removed from the list of retrieved Documents.

Tried to sort Documents with IDs 1,2, but got TypeError with the message: '<' not supported between instances of 'int' and 'str'

Expected behavior
Documents without the meta field are dropped. The example below should print ['1', '2'].

Additional context
When sorting fails, run() returns deduplicated_documents[:top_k], which includes the documents without the field:

This is not the case from #12952 (no document has the field), which is fixed. Here some documents have the field, but their values can't be sorted together.

To Reproduce

from haystack import Document
from haystack.components.rankers import MetaFieldRanker

ranker = MetaFieldRanker(meta_field="rating", missing_meta="drop")
docs = [
    Document(id="1", meta={"rating": 1}),
    Document(id="2", meta={"rating": "x"}),
    Document(id="3"),
]
print([d.id for d in ranker.run(documents=docs)["documents"]])
# ['1', '2', '3']

FAQ Check

• Have you had a look at our new FAQ page?

System:

• OS: Windows 11
• Haystack version: main (3.4.0-rc0)