Process Diagram is not loading over SSL in BRMS 5.3

Issue

After we configured SSL on JBoss, the BRMS Process Diagram is not loading.

We get the following error when accessing https://127.0.0.1:8443/designer/editor?profile=jbpm&uuid=d81c2cfb-9f06-45c0-b22a-10720ddcbff7

ERROR [stderr] (https://127.0.0.1:8443-2) java.lang.NullPointerException
ERROR [stderr] (https://127.0.0.1:8443-2)          at java.net.URLEncoder.encode(URLEncoder.java:205)
ERROR [stderr] (https://127.0.0.1:8443-2)          at org.jbpm.designer.web.preprocessing.impl.JbpmPreprocessingUnit.setupDefaultIcons(JbpmPreprocessingUnit.java:513)
ERROR [stderr] (https://127.0.0.1:8443-2)          at org.jbpm.designer.web.preprocessing.impl.JbpmPreprocessingUnit.preprocess(JbpmPreprocessingUnit.java:124)
ERROR [stderr] (https://127.0.0.1:8443-2)          at org.jbpm.designer.server.EditorHandler.doGet(EditorHandler.java:326)