Saving complex graph causes 500 server error

[Jrende]

Source code of offending image:

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Backend exception:

Caused by: java.lang.IllegalStateException: Not a JSON Object: null
	at com.google.gson.JsonElement.getAsJsonObject(JsonElement.java:90)
	at com.jrende.model.ImageOptimizer.makeFinalOutputOrigo(ImageOptimizer.java:28)
	at com.jrende.model.ImageOptimizer.optimizeGraph(ImageOptimizer.java:11)
	at com.jrende.resources.ImageResource.updateImageSource(ImageResource.java:106)
        ...