[BUG] 3D scatter plot reference planes with groups

[AIqbal94]

App 3D scatter plot

Describe the bug Reference place with group options throwing unexpected errors like

File "/myapp/myapp/routes/apps/threeDscatterplot.py", line 1905, in make_fig_output
    fig=make_figure(df,pa)
  File "/myapp/pyflaski/threeDscatterplot.py", line 455, in make_figure
    fig.add_trace(go.Surface(x=x_, y= y_.apply(lambda x: float(pa["y_axis_plane"])), z =  np.array([z]*length_data).transpose(),\
  File "/usr/local/lib/python3.7/dist-packages/pandas/core/series.py", line 4357, in apply
    return SeriesApply(self, func, convert_dtype, args, kwargs).apply()
  File "/usr/local/lib/python3.7/dist-packages/pandas/core/apply.py", line 1043, in apply
    return self.apply_standard()
  File "/usr/local/lib/python3.7/dist-packages/pandas/core/apply.py", line 1102, in apply_standard
    convert=self.convert_dtype,
  File "pandas/_libs/lib.pyx", line 2859, in pandas._libs.lib.map_infer
  File "/myapp/pyflaski/threeDscatterplot.py", line 455, in <lambda>
    fig.add_trace(go.Surface(x=x_, y= y_.apply(lambda x: float(pa["y_axis_plane"])), z =  np.array([z]*length_data).transpose(),\
ValueError: could not convert string to float: 

even when there's no input for y-plane