Fix: Default Mode In show_dash Causes TypeError

[yzhaoinuw]

This pull request aims to address the following bug.

Describe the bug 🖍️
When calling FigureResampler.show_dash() without specifying mode, the method raises TypeError: argument of type 'NoneType' is not iterable. Full error message is

TypeError                                 Traceback (most recent call last)
File c:\users\yzhao\python_projects\plotly-resampler\tests\test_show_dash.py:19
     16 fig = FigureResampler(go.Figure())
     17 fig.add_trace(go.Scattergl(), hf_x=x, hf_y=y)
---> 19 fig.show_dash(config={"scrollZoom": True})  # mode defaults to None

File ~\python_projects\plotly-resampler\plotly_resampler\figure_resampler\figure_resampler.py:610, in FigureResampler.show_dash(self, mode, config, init_dash_kwargs, graph_properties, **kwargs)
    608 # 2. Run the app
    609 height_param = "height" if mode == "inline_persistent" else "jupyter_height"
--> 610 if "inline" in mode and height_param not in kwargs:
    611     # If app height is not specified -> re-use figure height for inline dash app
    612     #  Note: default layout height is 450 (whereas default app height is 650)
    613     #  See: https://plotly.com/python/reference/layout/#layout-height
    614     fig_height = self.layout.height if self.layout.height is not None else 450
    615     kwargs[height_param] = fig_height + 18

TypeError: argument of type 'NoneType' is not iterable

Reproducing the bug 🔍

import numpy as np
import plotly.graph_objects as go
from plotly_resampler import FigureResampler


x = np.arange(100)
y = np.sin(x)

fig = FigureResampler(go.Figure())
fig.add_trace(go.Scattergl(), hf_x=x, hf_y=y)

fig.show_dash(config={"scrollZoom": True})  # mode defaults to None

Expected behavior 🔧
The figure opens in "external" mode, according to the show_dash docstring.

Environment information: (please complete the following information)

• OS: Windows 11
• Python environment:
  • Python version: 3.12
  • plotly-resampler environment: e.g.: Dash web app (Chrome)
• plotly-resampler version: 0.11.0

Additional context
The cause of the error is in the line if "inline" in mode and height_param not in kwargs: , which doesn't work when mode defaults to None but is regarded as a string here. We can fix this by setting mode to "external" before this line.