MG layers using filter containing double quotes cause legend error on startup

[chrisclaydon]

Load the attached MG package and view the Fusion layout. An error occurs on startup because the quotes in the filter for the layer's first theme get escaped twice.

i.e. " is replaced with
"

This causes an error when trying to parse the scale ranges. The error is displayed in a dialog, and the legend fails to render.

[chrisclaydon]

MG package that illustrates the problem

[pagameba]

(In [1653]) Fixes #161. addslashes was necessary when we were echo outputting the JSON response but var2json now escapes values so adding slashes for text is no longer required and in fact wrong because var2json escapes the slashes (causing this bug).