Docs: Update ListMacro.tid (#3754)

Addressing 2 issues.
1) If the caption field of a tiddler is empty
2) A note addressing no input titles resulting in a Filter Run as brought up on [Google Groups](https://groups.google.com/forum/?hl=en#!topic/tiddlywikidev/VNl_cwu_rIE)

editions/tw5.com/tiddlers/macros/ListMacro.tid

@@ -1,13 +1,15 @@
 caption: list-links
 created: 20140917083515996
-modified: 20180109171310659
+modified: 20190206000000000
 tags: Macros [[Core Macros]]
 title: list-links Macro
 type: text/vnd.tiddlywiki
 
 The <<.def list-links>> [[macro|Macros]] returns a formatted list of links to a [[selection of tiddlers|Title Selection]].
 
-If a tiddler has a <<.field caption>> field, this is shown instead of the tiddler's title.
+If a tiddler has a <<.field caption>> field, this is shown instead of the tiddler's title. If the caption field is empty, a blank entry is shown.
+
+Note: Each first [[step|Filter Step]] of a [[filter run|Filter Run]] not given any input titles receives the output of <$link to="all Operator">[all[tiddlers]]</$link> as its input. This means all the existing non-[[shadow|ShadowTiddlers]] tiddlers.
 
 !! Parameters