fix: don't allow empty scope

There seems to be a bug in treesitter that allows an infinite loop of
node parents, if the node is empty.
IBL doesn't care about the node if it's empty anyway, so we can just
ignore them.

fix #930

lua/ibl/scope.lua

@@ -72,7 +72,7 @@ M.get = function(bufnr, config)
     local include_node_types =
         utils.tbl_join(config.scope.include.node_type["*"] or {}, config.scope.include.node_type[lang] or {})
 
-    while node do
+    while node and node:byte_length() > 0 do
         local type = node:type()
 
         if