patch 8.2.4072: Vim9: compiling function fails when autoload is not loaded

Problem:    Vim9: compiling function fails when autoload script is not loaded
            yet.
Solution:   Depend on runtime loading.
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 311baca..ba81068 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -2227,6 +2227,16 @@
 		    }
 		    di = find_var_in_ht(ht, 0, iptr->isn_arg.string, TRUE);
 
+		    if (di == NULL && ht == get_globvar_ht())
+		    {
+			// may need to load autoload script
+			if (script_autoload(iptr->isn_arg.string, FALSE))
+			    di = find_var_in_ht(ht, 0,
+						   iptr->isn_arg.string, TRUE);
+			if (did_emsg)
+			    goto on_error;
+		    }
+
 		    if (di == NULL)
 		    {
 			SOURCING_LNUM = iptr->isn_lnum;