GridBox ncols not honored when rendering from a callable

[sdc50]

#297 ## ALL software version info

In [3]: param.__version__                                                                                                                                                                                                                                                                                                                                               
Out[3]: '1.10.0a2'

In [4]: pn.__version__                                                                                                                                                                                                                                                                                                                                                  
Out[4]: '0.10.0a2'

Description of expected behavior and the observed behavior

When a GridBox is first rendered dynamically (from a callable) then it first renders with only one column. After updating then the ncols parameter is respected.

Complete, minimal, self-contained example code that reproduces the issue

import random
import param
import panel as pn
pn.extension()

class Test(param.Parameterized):
    ncols = param.Integer(default=6)
    
    @param.depends('ncols')
    def grid(self):
        rcolor = lambda: "#%06x" % random.randint(0, 0xFFFFFF)
        return pn.GridBox(*[pn.pane.HTML(background=rcolor(), width=50, height=50) for i in range(24)], ncols=self.ncols)
    
    def panel(self):
        return pn.Column(
            self.param.ncols,
            self.grid,
        )
t = Test()
t.panel()

Screenshots or screencasts of the bug in action