patch 8.2.2253: Vim9: expr test fails

Problem:    Vim9: expr test fails.
Solution:   Add missing assignment.

src/userfunc.c

@@ -664,6 +664,8 @@ get_lambda_tv(
 		if (fp->uf_ret_type == NULL)
 		    goto errret;
 	    }
+	    else
+		fp->uf_ret_type = &t_unknown;
 	}
 
 	fp->uf_lines = newlines;

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2253,
 /**/
     2252,
 /**/