BUG#37528585 MySQL Shell Auto-complete crashes shell

An incorrect handling of non existing members in the autocompletion
chain caused the problem.

Change-Id: Id239be6f02290977c9d5c1ce37ca6152f7a3c63f

Author: rennox

mysqlshdk/scripting/polyglot/polyglot_context.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024, Oracle and/or its affiliates.
+ * Copyright (c) 2024, 2025, Oracle and/or its affiliates.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License, version 2.0,
@@ -148,13 +148,17 @@ const std::vector<std::string> &Polyglot_context::keywords() const {
 std::tuple<bool, polyglot::Store, std::string> Polyglot_context::get_member_of(
     const poly_value obj, const std::string &name) {
   auto member = get_member(thread(), obj, name);
-  auto type = to_string(thread(), type_info(member));
-  if (shcore::str_beginswith(type, "m.")) {
-    type = type.substr(2);
+  if (member) {
+    auto type = to_string(thread(), type_info(member));
+    if (shcore::str_beginswith(type, "m.")) {
+      type = type.substr(2);
+    }
+
+    return {is_executable(thread(), member), Store(thread(), member),
+            std::move(type)};
   }
 
-  return {is_executable(thread(), member), Store(thread(), member),
-          std::move(type)};
+  return {false, Store(nullptr), ""};
 }
 
 std::vector<std::pair<bool, std::string>> Polyglot_context::get_members_of(

unittest/completion_frontend_t.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2024, Oracle and/or its affiliates.
+ * Copyright (c) 2017, 2025, Oracle and/or its affiliates.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License, version 2.0,
@@ -2422,4 +2422,9 @@ TEST_F(Completer_frontend, bug_34365581) {
   execute("DROP SCHEMA ogÓrek;");
 }
 
+TEST_F(Completer_frontend, bug_37528585) {
+  execute("\\js");
+  EXPECT_NO_THROW(complete("shell.unexisting."));
+}
+
 }  // namespace mysqlsh