patch 9.1.1518: getcompletiontype() may crash

Problem:  getcompletiontype() crashes when no completion is available
          (after v9.1.1509).
Solution: Don't call set_expand_context() (zeertzjq)

fixes: #17681
closes: #17684

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index f38948c..60dbb47 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -1,4 +1,4 @@
-*builtin.txt*	For Vim version 9.1.  Last change: 2025 Jul 05
+*builtin.txt*	For Vim version 9.1.  Last change: 2025 Jul 06
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -4212,8 +4212,8 @@
 		|getcmdprompt()|, |getcmdcomplpat()| and |setcmdline()|.
 		Returns an empty string when completion is not defined.
 
-		To get the type of the command-line completion for the
-		specified string, use |getcompletiontype()|.
+		To get the type of the command-line completion for a specified
+		string, use |getcompletiontype()|.
 
 		Return type: |String|