FIX Firefox getCTM returning null

[jonathanlurie]

In the function initTransform(), the line

var screenCTM = svgElement.getCTM()

returns null on Firefox, making it impossible to do further operations, hence crashing the thing.

The fix checks if the matrix is null and if so replaces it by a fresh diagonal matrix.

Tested on MacOS 10.14:

• Firefox 69.0.3
• Chrome 83
• Safari 12

[anvaka]

Thank you! Patched in v9.2.5