patch 8.1.1355: obvious mistakes are accepted as valid expressions

Problem:    Obvious mistakes are accepted as valid expressions.
Solution:   Be more strict about parsing numbers. (Yasuhiro Matsumoto,
            closes #3981)
diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index 964c455..ff86d1c 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -558,7 +558,8 @@
 		{
 		    nrs[lnum - eap->line1].st_u.num.is_number = TRUE;
 		    vim_str2nr(s, NULL, NULL, sort_what,
-			       &nrs[lnum - eap->line1].st_u.num.value, NULL, 0);
+			&nrs[lnum - eap->line1].st_u.num.value,
+			NULL, 0, FALSE);
 		}
 	    }
 #ifdef FEAT_FLOAT