Set preedit cursor when cursor equals to 0
At least in fcitx, it is a common practice for certain input method to set cursor with zero to avoid popup window being moved around. Without setting it may end up in a unwanted position.
Pick-to: 6.3 6.2 5.15 Change-Id: I832fbb22d973b36ac4ab51570fc53bc2e4c3ed58 Reviewed-by: Liang Qi liang.qi@qt.io
Edited by Xuetian Weng