Clear selection on grid swap

Fixes #3290.

CHANGELOG.md

@@ -26,6 +26,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 - Tabstops not being reset with `reset`
+- Selection not cleared when switching between main and alt grid
 
 ## 0.4.2
 

alacritty_terminal/src/term/mod.rs

@@ -1195,6 +1195,7 @@ impl<T> Term<T> {
             let template = self.cursor.template;
             self.grid.region_mut(..).each(|c| c.reset(&template));
         }
+        self.grid.selection = None;
 
         self.alt = !self.alt;
         mem::swap(&mut self.grid, &mut self.alt_grid);