Skip checking `files` if no filename was provided to `syntax.get`

data/core/doc/init.lua

@@ -49,7 +49,7 @@ function Doc:reset_syntax()
     path = core.project_dir .. PATHSEP .. self.filename
   end
   if path then path = common.normalize_path(path) end
-  local syn = syntax.get(path or "", header)
+  local syn = syntax.get(path, header)
   if self.syntax ~= syn then
     self.syntax = syn
     self.highlighter:soft_reset()

data/core/syntax.lua

@@ -44,7 +44,7 @@ local function find(string, field)
 end
 
 function syntax.get(filename, header)
-  return find(filename, "files")
+  return (filename and find(filename, "files"))
       or (header and find(header, "headers"))
       or plain_text_syntax
 end