New issue by svenper on void-packages repository

https://github.com/void-linux/void-packages/issues/12885
Description: ### System

* xuname:  
  `Void 4.14.131_1 x86_64-musl GenuineIntel notuptodate hold rrnFFFFFFFFFFF`
* package:  
  firefox-67.0.4_1
  ibus-1.5.20_5

### Expected behavior

Selecting password fields do not crash the tab.

### Actual behavior

Selecting password fields crash the tab.

### Steps to reproduce the behavior

Install ibus, set the following variables in `.profile`, log in to an X session, and attempt to type into a a `<input type="password">` field [e.g. this example](https://bug1451466.bmoattachments.org/attachment.cgi?id=8965047). The ibus daemon does not have to be running. Chromium does not have the issue.
```text
export GTK_IM_MODULE=ibus
export XMODIFIERS=@im=ibus
export QT_IM_MODULE=ibus
```