fix: Link treated as checkbox

Author: kristijanhusak

corpus/basic.tst

@@ -1171,6 +1171,23 @@ List.11f  - No Checkbox [x ]
           (sym)
           (nl))))))
 
+================================================================================
+List.11g  - No Checkbox [[]
+================================================================================
+- [[ ]
+--------------------------------------------------------------------------------
+
+(document
+  body: (body
+    (list
+      (listitem
+        bullet: (bullet)
+        contents: (paragraph
+          (sym)
+          (sym)
+          (sym)
+          (nl))))))
+
 ================================================================================
 Directive.01  - Document
 ================================================================================