Update L.Polyline's _pxBounds when their stroke weight changes

[IvanSanchez]

Fixes #6514

[Jadaw1n]

Tested it, thanks for the quick fix!

[NielsHolt]

Hi
In version 1.5 Path.setStyle now calls this._updateBounds() if stroke is set in options
But it fails it setStyle is called before the path is added to the map
this._updateBounds using _rawPxBounds witch isn't set before _project is called

I think that the fix is to call this._project() instead of this._updateBounds() in setStyle

[t-sch]

I have a similar problem with Path.setStyle in a chart created with the leaflet-dvf addin. Here _updateBounds() isn't defined, too.
Probably not every L.Path derivate has _updateBounds() defined. I suggest at least a check before the call.