OSS-Fuzz issue 70081: pdfminersix:page_extraction_fuzzer: Uncaught exception in seek

[pietermarsman]

OSS-Fuzz discovered issue.

Details here. Monorail issue here.

 	ValueError: negative seek value -347
	Traceback (most recent call last):
	  File "fuzzing/page_extraction_fuzzer.py", line 26, in fuzz_one_input
	  File "pdfminer/high_level.py", line 209, in extract_pages
	  File "pdfminer/pdfpage.py", line 154, in get_pages
	  File "pdfminer/pdfdocument.py", line 706, in __init__
	  File "pdfminer/pdfdocument.py", line 972, in read_xref_from
	  File "pdfminer/psparser.py", line 549, in seek
	  File "pdfminer/psparser.py", line 208, in seek
	ValueError: negative seek value -347

Testcase