Merge pull request #1682 from fennerm/fix_prospector_e474

Fix prospector empty string error

ale_linters/python/prospector.vim

@@ -30,6 +30,10 @@ endfunction
 function! ale_linters#python#prospector#Handle(buffer, lines) abort
     let l:output = []
 
+    if empty(a:lines)
+        return []
+    endif
+
     let l:prospector_error = json_decode(join(a:lines, ''))
 
     for l:error in l:prospector_error.messages

test/handler/test_prospector_handler.vader

@@ -156,3 +156,8 @@ Execute(Ignoring trailing whitespace messages should work):
   \ '  ]',
   \ '}',
   \ ])
+
+Execute(The prospector handler should handle empty output):
+  AssertEqual
+  \ [],
+  \ ale_linters#python#prospector#Handle(bufnr(''), [])