Unexpected "forrtl: severe (157): Program Exception - access violation" exception during allocatable character array assignment

The following simple code compiler with no errors or warnings, however the assignment statement results in an "forrtl: severe (157): Program Exception - access violation" at run-time:

program p

   implicit none

   character(len=1), allocatable :: str(:)

   str = [ "" ]

   stop

end program p

forrtl: severe (157): Program Exception - access violation
Image              PC                Routine            Line        Source

p64.exe            000000013F7A7629  Unknown               Unknown  Unknown
p64.exe            000000013F782213  Unknown               Unknown  Unknown
p64.exe            000000013F781162  MAIN__                      7  p.f90
p64.exe            000000013F7AAA5E  Unknown               Unknown  Unknown
p64.exe            000000013F7AAD94  Unknown               Unknown  Unknown
kernel32.dll       00000000771A59DD  Unknown               Unknown  Unknown
ntdll.dll          00000000773DA631  Unknown               Unknown  Unknown
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Thanks,