patch 9.0.1051: after a failed CTRL-W ] next command splits window

Problem:    After a failed CTRL-W ] next command splits window.
Solution:   Reset postponed_split. (Rob Pilling, closes #11698)

src/testdir/test_window_cmd.vim

@@ -1911,4 +1911,17 @@ function Test_splitkeep_status()
   call VerifyScreenDump(buf, 'Test_splitkeep_status_1', {})
 endfunction
 
+function Test_new_help_window_on_error()
+  help change.txt
+  execute "normal! /CTRL-@\<CR>"
+  silent! execute "normal! \<C-W>]"
+
+  let wincount = winnr('$')
+  help 'mod'
+
+  call assert_equal(wincount, winnr('$'))
+  call assert_equal(expand("<cword>"), "'mod'")
+endfunction
+
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1051,
 /**/
     1050,
 /**/

src/window.c

@@ -559,6 +559,7 @@ newwindow:
 		// Execute the command right here, required when "wincmd ]"
 		// was used in a function.
 		do_nv_ident(Ctrl_RSB, NUL);
+		postponed_split = 0;
 		break;
 
 // edit file name under cursor in a new window
@@ -674,6 +675,7 @@ wingotofile:
 			// Execute the command right here, required when
 			// "wincmd g}" was used in a function.
 			do_nv_ident('g', xchar);
+			postponed_split = 0;
 			break;
 
 		    case 'f':	    // CTRL-W gf: "gf" in a new tab page