patch 8.0.1486: accessing invalid memory with "it"

Problem:    Accessing invalid memory with "it". (Dominique Pelle)
Solution:   Avoid going over the end of the line. (Christian Brabandt,
            closes #2532)

src/testdir/test_textobjects.vim

@@ -152,3 +152,16 @@ func Test_match()
   call assert_equal(3 , match('abc', '\zs', 3, 1))
   call assert_equal(-1, match('abc', '\zs', 4, 1))
 endfunc
+
+" This was causing an illegal memory access
+func Test_inner_tag()
+  new
+  norm ixxx
+  call feedkeys("v", 'xt')
+  insert
+x
+x
+.
+  norm it
+  q!
+endfunc