Fix PDF decryption issue for some empty password files #1940

Job	Run time
check (libclamav, (iana_cctld\|bytecode_api_\|bytecode_hooks\|rijndael\|yara\|inffixed\|inflate\|queue\|n...	48s
check (libclamav, (iana_cctld\|bytecode_api_\|bytecode_hooks\|rijndael\|yara\|inffixed\|inflate\|queue\|n...	17s
check (libfreshclam)	51s
check (libfreshclam)	19s
check (clamav-milter)	51s
check (clamav-milter)	20s
check (clambc)	44s
check (clambc)	21s
check (clamconf)	36s
check (clamconf)	20s
check (clamd)	35s
check (clamd)	35s
check (clamdscan)	30s
check (clamdscan)	21s
check (clamdtop)	20s
check (clamdtop)	20s
check (clamonacc, (c-thread-pool\|fts\|priv_fts))	35s
check (clamonacc, (c-thread-pool\|fts\|priv_fts))	23s
check (clamscan)	49s
check (clamscan)	21s
check (clamsubmit)	36s
check (clamsubmit)	18s
check (freshclam)	23s
check (freshclam)	23s
check (libfreshclam)	48s
check (libfreshclam)	17s
check (common)	35s
check (common)	21s
check (sigtool)	34s
check (sigtool)	21s
check (examples)	48s
check (examples)	20s
check (win32/compat)	26s
check (win32/compat)	26s
	16m 52s

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