patch 8.1.0963: illegal memory access when using 'incsearch'

Problem:    Illegal memory access when using 'incsearch'.
Solution:   Reset highlight_match when changing text. (closes #4022)

src/misc1.c

@@ -2854,6 +2854,11 @@ changed(void)
 	changed_int();
     }
     ++CHANGEDTICK(curbuf);
+
+#ifdef FEAT_SEARCH_EXTRA
+    // If a pattern is highlighted, the position may now be invalid.
+    highlight_match = FALSE;
+#endif
 }
 
 /*

src/testdir/dumps/Test_incsearch_change_01.dump

@@ -0,0 +1,9 @@
+|o+0&#ffffff0|n|e| @66
+|x+1&&| +0&&@68
+|t|h|r|e@1| @64
+|~+0#4040ff13&| @68
+|~| @68
+|~| @68
+|~| @68
+|~| @68
+|:+0#0000000&|%|s|/|X> @64

src/testdir/test_search.vim

@@ -981,6 +981,30 @@ func Test_incsearch_substitute_dump()
   call delete('Xis_subst_script')
 endfunc
 
+func Test_incsearch_with_change()
+  if !has('timers') || !exists('+incsearch') || !CanRunVimInTerminal()
+    return
+  endif
+
+  call writefile([
+	\ 'set incsearch hlsearch scrolloff=0',
+	\ 'call setline(1, ["one", "two ------ X", "three"])',
+	\ 'call timer_start(200, { _ -> setline(2, "x")})',
+	\ ], 'Xis_change_script')
+  let buf = RunVimInTerminal('-S Xis_change_script', {'rows': 9, 'cols': 70})
+  " Give Vim a chance to redraw to get rid of the spaces in line 2 caused by
+  " the 'ambiwidth' check.
+  sleep 100m
+
+  " Highlight X, it will be deleted by the timer callback.
+  call term_sendkeys(buf, ':%s/X')
+  call VerifyScreenDump(buf, 'Test_incsearch_change_01', {})
+  call term_sendkeys(buf, "\<Esc>")
+
+  call StopVimInTerminal(buf)
+  call delete('Xis_change_script')
+endfunc
+
 " Similar to Test_incsearch_substitute_dump() for :sort
 func Test_incsearch_sort_dump()
   if !exists('+incsearch')

src/version.c

@@ -779,6 +779,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    963,
 /**/
     962,
 /**/