Fix newlines causing bad rendering artifacts

The unicode-width crate has started to consider newlines to have a width
of 1 instead of 0.

src/widthdb.rs

@@ -47,9 +47,13 @@ impl WidthDb {
         if grapheme == "\t" {
             return self.tab_width_at_column(col);
         }
+        if grapheme.chars().any(|c| c.is_ascii_control()) {
+            return 0; // See measure_widths function
+        }
         if !self.active {
             return grapheme.width() as u8;
         }
+
         if let Some(width) = self.known.get(grapheme) {
             *width
         } else {