fix: do not send data to closed stream (#2746)

This commit fixes the following error:

E5108: Error executing lua: Vim:Can't send data to closed stream
stack traceback:
[C]: in function 'chansend'
/lua/telescope/previewers/term_previewer.lua:224: in function '_send_input'
/lua/telescope/previewers/previewer.lua:85: in function 'send_input'
/lua/telescope/previewers/term_previewer.lua:238: in function '_scroll_fn'
/lua/telescope/previewers/previewer.lua:93: in function 'scroll_fn'
/lua/telescope/actions/set.lua:249: in function 'run_replace_or_original'
/lua/telescope/actions/mt.lua:65: in function 'scroll_previewer'
/lua/telescope/actions/init.lua:222: in function 'run_replace_or_original'

This happens when previewers.new_termopen_previewer()'s get_command()
ends without pagination.

lua/telescope/previewers/term_previewer.lua

@@ -221,6 +221,10 @@ previewers.new_termopen_previewer = function(opts)
 
       local term_id = get_term_id(self)
       if term_id then
+        if not utils.job_is_running(term_id) then
+          return
+        end
+
         vim.fn.chansend(term_id, termcode)
       end
     end