core: fix access to uninitialized memory in NMIPConfig

The string array returned by nm_l3_config_data_get_searches() is not
NULL-terminated; we need to pass the exact length to
nm_utils_buf_utf8safe_escape_strv() instead of letting the function
scan for the NULL terminator.

Fix the following error reported by valgrind:

  Conditional jump or move depends on uninitialised value(s)
     at 0x4B287DB: g_strv_length (gstrfuncs.c:2948)
     by 0x6EBDBE: nm_utils_buf_utf8safe_escape_strv (nm-shared-utils.c:3047)
     by 0x59A3F1: get_property_ip (nm-ip-config.c:198)
     by 0x4A6E150: UnknownInlinedFun (gobject.c:2140)
     by 0x4A6E150: g_object_get_property (gobject.c:3454)
     by 0x56FB1A: nm_dbus_utils_get_property (nm-dbus-utils.c:95)
     by 0x44B343: _obj_get_property (nm-dbus-manager.c:880)
     by 0x44DC4F: _nm_dbus_manager_obj_notify (nm-dbus-manager.c:1201)
     by 0x56EE77: dispatch_properties_changed (nm-dbus-object.c:253)
     by 0x4A5BF1E: g_object_notify_queue_thaw.lto_priv.0 (gobject.c:755)
     by 0x5997BD: _handle_l3cd_changed (nm-ip-config.c:837)
     by 0x59A129: _l3cfg_notify_cb (nm-ip-config.c:147)
     by 0x4A5B649: g_closure_invoke (gclosure.c:834)

Fixes: 522a7d6baf ('nm-ip-config: escape searches when exposing to dbus')

src/core/nm-ip-config.c

@@ -197,7 +197,7 @@ get_property_ip(GObject *object, guint prop_id, GValue *value, GParamSpec *pspec
         if (strv) {
             strv = nm_utils_buf_utf8safe_escape_strv(
                 strv,
-                -1,
+                len,
                 NM_UTILS_STR_UTF8_SAFE_FLAG_ESCAPE_CTRL
                     | NM_UTILS_STR_UTF8_SAFE_FLAG_ESCAPE_NON_ASCII,
                 &to_free);