pdfunite crashed with SIGABRT in main()

Following crash was caught by Apport in Ubuntu 20.04. Crash was triggered by running pdfunite UE7.pdf UE7-append.pdf UE7.pdf:

Stacktrace:
 #0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
         set = {__val = {0, 93928966115392, 55, 93928999065392, 7, 93928999065280, 93928999065376, 140301947519011, 206158430256, 140723515419936, 140723515419744, 9846784182788627200, 121, 18446744073709551488, 0, 140301952796440}}
         pid = <optimized out>
         tid = <optimized out>
         ret = <optimized out>
 #1  0x00007f9a97ad8859 in __GI_abort () at abort.c:79
         save_stage = 1
         act = {__sigaction_handler = {sa_handler = 0xd, sa_sigaction = 0xd}, sa_mask = {__val = {140723515419896, 13, 140723515419896, 0, 9846784182788627200, 0, 93928999060624, 93928999057376, 140723515420512, 140723515420480, 93928999056464, 140723515420672, 140301952314607, 93928999060896, 93928999060624, 93928999058544}}, sa_flags = -1935704928, sa_restorer = 0x7ffcbf25ef40}
         sigs = {__val = {32, 0 <repeats 15 times>}}
 #2  0x0000556d8aa89aa6 in ?? ()
 No symbol table info available.
 #3  0x0000556d8aa87d28 in main ()
 No symbol table info available.
StacktraceAddressSignature: /usr/bin/pdfunite:6:/usr/lib/x86_64-linux-gnu/libc-2.31.so+859:/usr/bin/pdfunite+2aa6:/usr/bin/pdfunite+d28
StacktraceSource:
 #0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
   [Error: raise.c was not found in source tree]
 #1  0x00007f9a97ad8859 in __GI_abort () at abort.c:79
   [Error: abort.c was not found in source tree]
 #2  0x0000556d8aa89aa6 in ?? ()
 #3  0x0000556d8aa87d28 in main ()
 
StacktraceTop:
 ?? ()
 main ()
Tags: focal wayland-session
ThreadStacktrace:
 .
 Thread 1 (Thread 0x7f9a96e847c0 (LWP 73202)):
 #0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
         set = {__val = {0, 93928966115392, 55, 93928999065392, 7, 93928999065280, 93928999065376, 140301947519011, 206158430256, 140723515419936, 140723515419744, 9846784182788627200, 121, 18446744073709551488, 0, 140301952796440}}
         pid = <optimized out>
         tid = <optimized out>
         ret = <optimized out>
 #1  0x00007f9a97ad8859 in __GI_abort () at abort.c:79
         save_stage = 1
         act = {__sigaction_handler = {sa_handler = 0xd, sa_sigaction = 0xd}, sa_mask = {__val = {140723515419896, 13, 140723515419896, 0, 9846784182788627200, 0, 93928999060624, 93928999057376, 140723515420512, 140723515420480, 93928999056464, 140723515420672, 140301952314607, 93928999060896, 93928999060624, 93928999058544}}, sa_flags = -1935704928, sa_restorer = 0x7ffcbf25ef40}
         sigs = {__val = {32, 0 <repeats 15 times>}}
 #2  0x0000556d8aa89aa6 in ?? ()
 No symbol table info available.
 #3  0x0000556d8aa87d28 in main ()
 No symbol table info available.

Full apport file: _usr_bin_pdfunite.1000.crash.txt