patch 8.0.1257: no test for fix of undefined behavior

Problem:    No test for fix of undefined behavior.
Solution:   Add a test. (closes #2255)

Author: brammool

src/testdir/test_search.vim

@@ -697,3 +697,7 @@ func Test_search_undefined_behaviour()
   call term_sendkeys(g:buf, ":qa!\<cr>")
   bwipe!
 endfunc
+
+func Test_search_undefined_behaviour2()
+  call search("\%UC0000000")
+endfunc

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1257,
 /**/
     1256,
 /**/