Improve checking for unterminated string in mirb

tools/mirb/mirb.c

@@ -38,9 +38,6 @@ is_code_block_open(struct mrb_parser_state *parser)
 {
   int code_block_open = FALSE;
 
-  /* check for unterminated string */
-  if (parser->lex_strterm) return TRUE;
-
   /* check for heredoc */
   if (parser->heredoc_starts_nextline) return TRUE;
   if (parser->heredoc_end_now) {
@@ -70,6 +67,9 @@ is_code_block_open(struct mrb_parser_state *parser)
     return code_block_open;
   }
 
+  /* check for unterminated string */
+  if (parser->lex_strterm) return TRUE;
+
   switch (parser->lstate) {
 
   /* all states which need more code */