respect reverse video attributes for inferred cells

In the case where the cells vec is shorter than the line width,
we need to ensure that we render the inverse video background
color if that mode is in effect.

refs: #133

wezterm-gui/src/termwindow/render.rs

@@ -674,14 +674,20 @@ impl super::TermWindow {
         // open a vim split horizontally.  Backgrounding vim would leave
         // the right pane with its prior contents instead of showing the
         // cleared lines from the shell in the main screen.
+        let clear_bg = if params.line.is_reverse() {
+            params.foreground
+        } else {
+            params.default_bg
+        };
+
         for cell_idx in 0..num_cols {
             let mut quad =
                 match quads.cell(cell_idx + params.pos.left, params.line_idx + params.pos.top) {
                     Ok(quad) => quad,
                     Err(_) => break,
                 };
 
-            quad.set_bg_color(params.default_bg);
+            quad.set_bg_color(clear_bg);
             quad.set_texture(params.white_space);
             quad.set_image_texture(params.white_space);
             quad.set_texture_adjust(0., 0., 0., 0.);