Open a report without defined filepath

[Benjamin Jakimow]

enmapbox.processing.report.Report

open() routine uses self.filename which might be undefined (e.g. after unpickle a model file) self.filename is neither checked nor set by default

recommended solution: use default temp path or required a filepath as argument

[Andreas Janz]

This is the correct usage:

image = Type()
image.report().saveHTML().open()