NPE in PDAcroForm.getField() if the /Fields entry is missing

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I get a lot of weird documents. When I try to set a particular field value, some of them throw NullPointerExceptions from line PDAcroForm.getField(), line 291:

287: COSArray fields =
288: (COSArray) acroForm.getDictionaryObject(
289: COSName.getPDFName("Fields"));
290:
291: for (int i = 0; i < fields.size() && retval == null; i++)
292:{

To avoid this, at first I was calling PDAcroForm.getFields() and checking that to see if that was NULL but I realized that it would usually create a new fields array to return which seemed wasteful.

Is the most efficient way to avoid this to first call:
COSArray fields = (COSArray) acroForm.getDictionaryObject( COSName.getPDFName("Fields"));
myself and check if that is NULL?

Secondary Question:
The method PDAcroForm.getFields() does a not-NULL check of fields before calling fields.size().
Is there a reason that this check is not performed in getField()?