Reinstate '!=' fix by Bruce Evans.  The original commit message from parse.c(1.9) was:
Reinstate '!=' fix by Bruce Evans.  The original commit message from
parse.c(1.9) was:

revision 1.9
date: 1996/09/12 03:03:25;  author: bde;  state: Exp;  lines: +7 -6
Fixed handling of `!=' assignment.  Don't warn if the shell's output is
null, but warn if there was an error reading it.

Suggested by: Bruce Evans <bde@zeta.org.au>

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