Calling `rule.getDerivedUnits()` on Assignmentrule for japl in the biomodel BIOMD0000000327.xml results in java.lang.NullPointerException

[matthiaskoenig]

Calling rule.getDerivedUnits() on Assignmentrule for japl in the biomodel BIOMD0000000327.xml results in the following parsing error:

BIOMD0000000327.zip

assignmentRule [ metaid="_126623" variable="japl"]
java.lang.NullPointerException: Cannot invoke "org.sbml.jsbml.ASTNode.getIndex(javax.swing.tree.TreeNode)" because "parent" is null
	at org.sbml.jsbml.util.converters.ExpandFunctionDefinitionConverter$3.accepts(ExpandFunctionDefinitionConverter.java:241)
	at org.sbml.jsbml.AbstractTreeNode.filter(AbstractTreeNode.java:362)
	at org.sbml.jsbml.AbstractTreeNode.filter(AbstractTreeNode.java:375)
	at org.sbml.jsbml.AbstractTreeNode.filter(AbstractTreeNode.java:375)
	at org.sbml.jsbml.AbstractTreeNode.filter(AbstractTreeNode.java:375)
	at org.sbml.jsbml.AbstractTreeNode.filter(AbstractTreeNode.java:375)
	at org.sbml.jsbml.AbstractTreeNode.filter(AbstractTreeNode.java:375)
	at org.sbml.jsbml.AbstractTreeNode.filter(AbstractTreeNode.java:375)
	at org.sbml.jsbml.AbstractTreeNode.filter(AbstractTreeNode.java:353)
	at org.sbml.jsbml.AbstractTreeNode.filter(AbstractTreeNode.java:345)
	at org.sbml.jsbml.util.converters.ExpandFunctionDefinitionConverter.replaceAll(ExpandFunctionDefinitionConverter.java:232)
	at org.sbml.jsbml.util.converters.ExpandFunctionDefinitionConverter.access$000(ExpandFunctionDefinitionConverter.java:59)
	at org.sbml.jsbml.util.converters.ExpandFunctionDefinitionConverter$2.accepts(ExpandFunctionDefinitionConverter.java:185)
	at org.sbml.jsbml.AbstractTreeNode.filter(AbstractTreeNode.java:362)
	at org.sbml.jsbml.AbstractTreeNode.filter(AbstractTreeNode.java:375)
	at org.sbml.jsbml.util.converters.ExpandFunctionDefinitionConverter.expandFunctionDefinition(ExpandFunctionDefinitionConverter.java:149)
	at org.sbml.jsbml.AbstractMathContainer.getDerivedUnitDefinition(AbstractMathContainer.java:185)
	at org.sbml.jsbml.AbstractMathContainer.getDerivedUnits(AbstractMathContainer.java:229)
``