fix stringify

Author: aspeddro

analysis/src/Commands.ml

@@ -260,7 +260,7 @@ let format ~path =
 let diagnosticSyntax ~path =
   print_endline
     (match Diagnostics.document_syntax ~path with
-    | [] -> Protocol.null
+    | [] -> "[]"
     | d -> Protocol.array d)
 
 let test ~path =

analysis/src/Protocol.ml

@@ -132,7 +132,7 @@ let stringifyCodeAction ca =
 
 let stringifyDiagnostic d =
   Printf.sprintf {|{
-  "range: %s,
+  "range": %s,
   "message": "%s",
   "severity": %d,
 }|}