#574 Do not restore items with no columns for highlights from hidden buffers

test/test_highlight_placement.vader

@@ -98,8 +98,10 @@ Execute(Highlights set by ALE should be removed when buffer cleanup is done):
 
 Execute(Highlights should be cleared when buffers are hidden):
   call ale#engine#InitBufferInfo(bufnr('%'))
+  " The second item should be ignored, as it has no column infomration.
   let g:ale_buffer_info[bufnr('%')].loclist =  [
   \ {'bufnr': bufnr('%'), 'type': 'E', 'lnum': 3, 'col': 2},
+  \ {'bufnr': bufnr('%'), 'type': 'E', 'lnum': 4, 'col': 0},
   \]
   call ale#highlight#SetHighlights(
   \ bufnr('%'),