fixed zero-sized buffer condition check

buffer.go

@@ -42,7 +42,7 @@ func (b *Buffer[T]) y(y int) int {
 
 // Set sets the value at position (x,y) to c
 func (b *Buffer[T]) Set(x, y int, v T) {
-	if b.width >= 0 && b.height >= 0 {
+	if b.width > 0 && b.height > 0 {
 		b.data[b.y(y)][b.x(x)] = v
 	}
 }

buffer_test.go

@@ -19,6 +19,6 @@ func TestSub(t *testing.T) {
 }
 
 func TestSet(t *testing.T) {
-	b := NewBuffer(10, 10, ' ')
-	b.Set(11, 0, 'a')
+	b := NewBuffer(0, 0, ' ')
+	b.Set(0, 0, 'a')
 }