Fix [nil] is passed to auto_indent_proc when exit with CTRL+d (#571)

* Fix [nil] is passed to auto_indent_proc when exit with CTRL+d

Fix it #556

* not call auto_indent_proc when Ctrl+d.

see: #571 (comment)

Author: osyo-manga

lib/reline/line_editor.rb

@@ -1605,7 +1605,7 @@ def input_key(key)
     else
       @just_cursor_moving = false
     end
-    if @is_multiline and @auto_indent_proc and not simplified_rendering?
+    if @is_multiline and @auto_indent_proc and not simplified_rendering? and @line
       process_auto_indent
     end
   end