patch 8.2.1504: Vim9: white space checks are only done for a :def function

Problem:    Vim9: white space checks are only done for a :def function.
Solution:   Also do checks at the script level.  Adjust the name of a few
            error messages.
diff --git a/src/vim9script.c b/src/vim9script.c
index b9dc5d7..e86150a 100644
--- a/src/vim9script.c
+++ b/src/vim9script.c
@@ -532,7 +532,7 @@
     }
     if (!VIM_ISWHITE(p[1]))
     {
-	semsg(_(e_white_space_required_after), ":");
+	semsg(_(e_white_space_required_after_str), ":");
 	return arg + STRLEN(arg);
     }
     name = vim_strnsave(arg, p - arg);