Update runtime files
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index e6c9992..ad50bfc 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -1,4 +1,4 @@
-*options.txt* For Vim version 8.1. Last change: 2019 Jun 27
+*options.txt* For Vim version 8.1. Last change: 2019 Jul 06
VIM REFERENCE MANUAL by Bram Moolenaar
@@ -1142,8 +1142,10 @@
set bexpr=MyBalloonExpr()
set ballooneval
<
- Also see |balloon_show()|, can be used if the content of the balloon
- is to be fetched asynchronously.
+ Also see |balloon_show()|, it can be used if the content of the balloon
+ is to be fetched asynchronously. In that case evaluating
+ 'balloonexpr' should result in an empty string. If you get a balloon
+ with only "0" you probably didn't return anything from your function.
NOTE: The balloon is displayed only if the cursor is on a text
character. If the result of evaluating 'balloonexpr' is not empty,
@@ -1155,7 +1157,7 @@
This option cannot be set in a modeline when 'modelineexpr' is off.
It is not allowed to change text or jump to another window while
- evaluating 'balloonexpr' |textlock|.
+ evaluating 'balloonexpr', see |textlock|.
To check whether line breaks in the balloon text work use this check: >
if has("balloon_multiline")