bdiff: fix malloc(0) issue in fixws()
If fixws() is called on a zero-length string, malloc(0) is called and
expected to return a pointer. Which it does on e.g. Linux. AIX returns
NULL, which it is also legal, but the malloc() is then assumed to have
failed. So ensure a valid pointer is always returned.
Simple commands:
$ echo foo
foo
$ printf 'oh no'
oh no (no-eol)
$ printf 'bar\nbaz\n' | cat
bar
baz
Multi-line command:
$ foo() {
> echo bar
> }
$ foo
bar
Return codes before inline python:
$ sh -c 'exit 1'
[1]
Doctest commands:
>>> print 'foo'
foo
$ echo interleaved
interleaved
>>> for c in 'xyz':
... print c
x
y
z
>>> print
Regular expressions:
$ echo foobarbaz
foobar.* (re)
$ echo barbazquux
.*quux.* (re)
Globs:
$ printf '* \\foobarbaz {10}\n'
\* \\fo?bar* {10} (glob)
Literal match ending in " (re)":
$ echo 'foo (re)'
foo (re)
Exit code:
$ (exit 1)
[1]