patch 8.2.2061: Vim9: E1030 error when using empty string for term_sendkeys()

Problem:    Vim9: E1030 error when using empty string for term_sendkeys().
Solution:   Don't check for an invalid type unless the terminal can't be
            found. (closes #7382)
diff --git a/src/terminal.c b/src/terminal.c
index 6be7579..32e52ee 100644
--- a/src/terminal.c
+++ b/src/terminal.c
@@ -4595,12 +4595,12 @@
 {
     buf_T *buf;
 
-    (void)tv_get_number(&argvars[0]);	    // issue errmsg if type error
     ++emsg_off;
     buf = tv_get_buf(&argvars[0], FALSE);
     --emsg_off;
     if (buf == NULL || buf->b_term == NULL)
     {
+	(void)tv_get_number(&argvars[0]);    // issue errmsg if type error
 	ch_log(NULL, "%s: invalid buffer argument", where);
 	return NULL;
     }