Dialog glitch with pancurses backend on Alacritty

I am reporting a bug. Specifically, it's a graphical glitch that happens only under specific conditions.

# Problem description

The border of the dialog view will render incorrectly and produce glitches at the end of the line.

```rust
siv.add_layer(
Dialog::new()
.title("A dialog")
.content(TextView::new_with_content(TextContent::new(
"Some text"
)))
.button("Back", |s| {
let _ = s.pop_layer();
}),
)
```

# Environment

* Operating system: macOS
* Backend used: pancurses (seems to work fine with the other ones)
* Virtual terminal: Alacritty 0.4.2 (seems to work fine with Terminal.app and iTerm)
* Current locale: en_GB.UTF-8
* Cursive version: 0.14 (from crates.io)