Fix a compiler bug, keypad ENTER now inserts a newline

TODO.FACTOR.txt

@@ -1,11 +1,7 @@
 + 0.85:
 
-- ENTER key on keypad should do something
 - pane output in UI should use less memory
 - signal 4 on datastack underflow on mac intel??
-- why is a 'null' type inferred for the output of foo in
-  : foo f ;
-  : bar foo 4 4 = and ;
 - faster I/O
 - buffer-ptr should be an alien
 - faster Unix stream-read#

library/compiler/optimizer/class-infer.factor

@@ -155,7 +155,8 @@ DEFER: (infer-classes)
     ] 2each ;
 
 : merge-value-class ( # nodes -- class )
-    [ swap node-class# ] map-with null [ class-or ] reduce ;
+    [ swap node-class# ] map-with
+    null [ class-or ] reduce ;
 
 : annotate-merge ( nodes values -- )
     dup length
@@ -164,9 +165,13 @@ DEFER: (infer-classes)
 
 : merge-children ( node -- )
     dup node-successor dup #merge? [
-        node-out-d <reversed>
-        >r node-children [ last-node ] map r>
-        annotate-merge
+        over node-children empty? [
+            2drop
+        ] [
+            node-out-d <reversed>
+            >r node-children [ last-node ] map r>
+            annotate-merge
+        ] if
     ] [
         2drop
     ] if ;

library/ui/text/commands.factor

@@ -71,6 +71,7 @@ editor {
         "Editing"
         { "Insert newline" T{ key-down f f "RETURN" } [ "\n" swap user-input ] }
         { "Insert newline" T{ key-down f { S+ } "RETURN" } [ "\n" swap user-input ] }
+        { "Insert newline" T{ key-down f "ENTER" } [ "\n" swap user-input ] }
         { "Delete next character" T{ key-down f f "DELETE" } [ T{ char-elt } editor-delete ] }
         { "Delete previous character" T{ key-down f f "BACKSPACE" } [ T{ char-elt } editor-backspace ] }
         { "Delete previous word" T{ key-down f { C+ } "DELETE" } [ T{ word-elt } editor-delete ] }