patch 9.1.0576: tests: still an issue with test_gettext_make

Problem:  tests: still an issue with test_gettext_make
          (after v9.1.0570)
Solution: Compare the getenv() output against v:null to verify
          that $GETTEXT_PATH was set or not (Ken Takata)

closes: #15236

Signed-off-by: Ken Takata <kentkt@csc.jp>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_gettext_make.vim b/src/testdir/test_gettext_make.vim
index 22b04745..1242fa4 100644
--- a/src/testdir/test_gettext_make.vim
+++ b/src/testdir/test_gettext_make.vim
@@ -6,7 +6,7 @@
 func Test_gettext_makefile()
   cd ../po
   if has('win32')
-    if getenv('GETTEXT_PATH') == ''
+    if getenv('GETTEXT_PATH') == v:null
       throw 'Skipped: %GETTEXT_PATH% is not set.'
     endif
     call system('nmake.exe -f Make_mvc.mak "VIMPROG=' .. getenv('VIMPROG') ..
diff --git a/src/version.c b/src/version.c
index c9113e6..9dbe651 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    576,
+/**/
     575,
 /**/
     574,