unix: fix uv_os_environ() null pointer check
unix: fix uv_os_environ() null pointer check

Check the pointer to the allocated memory, not the pointer to the
pointer of the allocated memory. Previously, a failed allocation of
*envitems would lead to a NULL pointer dereference.

PR-URL: https://github.com/libuv/libuv/pull/2778
Reviewed-By: Richard Lau <8193d74c06330af7778ef55510160e4e561ed6a1@uk.ibm.com>
Reviewed-By: Anna Henningsen <2bc1ecb410e142bce83bce6f212b41e1781536dc@addaleax.net>
Reviewed-By: Colin Ihrig <838f779c91673db29b8572ea3f54d191d3878ae2@gmail.com>
Reviewed-By: Bartosz Sosnowski <aa4e0bd35c562885f21ad74b171c23cfc4370e31@janeasystems.com>

unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso