patch 8.0.0446: the ";" command does not work after some characters

Problem:    The ";" command does not work after characters with a lower byte
            that is NUL.
Solution:   Properly check for not having a previous character. (Hirohito
            Higashi)

src/testdir/test_alot_utf8.vim

@@ -6,6 +6,7 @@
 " files, so that they can be run by themselves.
 
 set belloff=all
+source test_charsearch_utf8.vim
 source test_expr_utf8.vim
 source test_matchadd_conceal_utf8.vim
 source test_regexp_utf8.vim

src/testdir/test_charsearch_utf8.vim

@@ -0,0 +1,44 @@
+" Tests for related f{char} and t{char} using utf-8.
+if !has('multi_byte')
+  finish
+endif
+
+" Test for t,f,F,T movement commands
+function! Test_search_cmds()
+  new!
+  call setline(1, "・最初から最後まで最強のVimは最高")
+  1
+  normal! f最
+  call assert_equal([0, 1, 4, 0], getpos('.'))
+  normal! ;
+  call assert_equal([0, 1, 16, 0], getpos('.'))
+  normal! 2;
+  call assert_equal([0, 1, 43, 0], getpos('.'))
+  normal! ,
+  call assert_equal([0, 1, 28, 0], getpos('.'))
+  bw!
+endfunction
+
+" vim: shiftwidth=2 sts=2 expandtab
+" Tests for related f{char} and t{char} using utf-8.
+if !has('multi_byte')
+  finish
+endif
+
+" Test for t,f,F,T movement commands
+function! Test_search_cmds()
+  new!
+  call setline(1, "・最初から最後まで最強のVimは最高")
+  1
+  normal! f最
+  call assert_equal([0, 1, 4, 0], getpos('.'))
+  normal! ;
+  call assert_equal([0, 1, 16, 0], getpos('.'))
+  normal! 2;
+  call assert_equal([0, 1, 43, 0], getpos('.'))
+  normal! ,
+  call assert_equal([0, 1, 28, 0], getpos('.'))
+  bw!
+endfunction
+
+" vim: shiftwidth=2 sts=2 expandtab