If the variable does not exist, just return.

dlls/kernel/tests/environ.c

@@ -215,15 +215,13 @@ static void test_ExpandEnvironmentStringsA()
 {
     char buf[256], buf1[256];
     DWORD ret_size, ret_size1;
-    int error;
 
     ret_size1 = GetWindowsDirectoryA(buf1,256);
     ok ((ret_size1 >0) && (ret_size1<256), "GetWindowsDirectory Failed\n");
     ret_size = ExpandEnvironmentStringsA("%SystemRoot%",buf,sizeof(buf));
-    error = GetLastError();
-    ok(!strcmp(buf, buf1),
-       "ExpandEnvironmentStrings failed %s vs %s. GetLastError() == %d, ret_size = %ld\n",
-       buf, buf1, error, ret_size);
+    if (ERROR_ENVVAR_NOT_FOUND == GetLastError())
+        return;
+    ok(!strcmp(buf, buf1), "ExpandEnvironmentStrings failed %s vs %s. ret_size = %ld\n", buf, buf1, ret_size);
 }
 
 START_TEST(environ)