fix(barchart): avoid divide by zero in rendering (#525)

Fixes: #521

src/widgets/barchart.rs

@@ -506,10 +506,15 @@ impl<'a> Widget for BarChart<'a> {
         buf.set_style(area, self.style);
 
         self.render_block(&mut area, buf);
-
+        if area.area() == 0 {
+            return;
+        }
         if self.data.is_empty() {
             return;
         }
+        if self.bar_width == 0 {
+            return;
+        }
 
         let label_height = self.label_height();
         if area.height <= label_height {
@@ -1180,4 +1185,16 @@ mod tests {
         ]);
         assert_buffer_eq!(buffer, expected);
     }
+
+    #[test]
+    fn handles_zero_width() {
+        // this test is to ensure that a BarChart with zero bar / gap width does not panic
+        let chart = BarChart::default()
+            .data(&[("A", 1)])
+            .bar_width(0)
+            .bar_gap(0);
+        let mut buffer = Buffer::empty(Rect::new(0, 0, 0, 10));
+        chart.render(buffer.area, &mut buffer);
+        assert_buffer_eq!(buffer, Buffer::empty(Rect::new(0, 0, 0, 10)));
+    }
 }