fixed hang issue with --headless and -r option specified

Calling the do_more_prompt function in headless mode will freeze neovim because it is eventally in the input-accepting state (the same as waiting for --more--).

Author: Code-Hex

src/nvim/message.c

@@ -2577,7 +2577,7 @@ static int do_more_prompt(int typed_char)
   // We get called recursively when a timer callback outputs a message. In
   // that case don't show another prompt. Also when at the hit-Enter prompt
   // and nothing was typed.
-  if (entered || (State == HITRETURN && typed_char == 0)) {
+  if (headless_mode || entered || (State == HITRETURN && typed_char == 0)) {
     return false;
   }
   entered = true;