shareX = T produces blank plot when plotting non-square subplots

In the code below when subplot is 4x3 with shareX = T, it produces a blank plot. If you make it 4x4 it works fine (or if you set shareX = F).

p <- plot_ly(y = ~rnorm(50), type = "box", name = "A") %>%
  add_trace(y = ~rnorm(50, 1), name = "B") %>%
  add_trace(y = ~rnorm(50, 1), name = "C") %>%
  add_trace(y = ~rnorm(50, 1), name = "D")

p <- subplot(p,p,p,p, shareY = TRUE)

p <- subplot(p,p,p, nrows=3, shareX = TRUE) %>%
  layout(showlegend = FALSE)

p

使用 issue 中的 R 示例重现空白输出，对比启用或禁用 shareX 时的 4x3 和 4x4 subplot 布局。跟踪 plotly.R 使用的 subplot 和共享坐标轴处理方式，然后为非方形情况添加或更新回归测试。当 4x3 共享 X 轴示例能够渲染出图表而不是空白结果时，即表示完成。