Fix: skip empty annotation bbox (#1665)
Address: https://github.com/Unstructured-IO/unstructured/issues/1663
## Summary
While trying to find how overlap between a element bbox and annotation
bbox, we find the intersection of two bboxes and divide it by the size
of annotation bbox, this will cause a zero division error if size of
annotation bbox is 0.
* this PR fix the zero division error for function
`check_annotations_within_element`
* also fix error: `TypeError: unsupported operand type(s) for -: 'float'
and 'NoneType'` by stop inserting empty word with None bbox into list of
words in function `get_word_bounding_box_from_element`
## Test
reproduce with code and document as the user mentioned and should see no
error:
```
from unstructured.partition.auto import partition
elements = partition(
filename="./IZSAM8.2_221012.pdf",
strategy="fast",
)
```
