NPE in ComplexContentDiffGenerator

[ff-wl]

I've encountered a NullPointerException in ComplexContentDiffGenerator:

soa-model/core/src/main/groovy/com/predic8/schema/diff/ComplexContentDiffGenerator.groovy

Line 61 in 9e7acdf

if(a.derivation.model && b.derivation.model

a.derivation was null.

derivation is not mandatory in ComplexContent, if this branch is taken while creating:

soa-model/core/src/main/groovy/com/predic8/schema/ComplexContent.groovy

Lines 58 to 63 in 9e7acdf

	} else {
	// It is a build in type from XML Schema
	restriction = RestrictionUtil.getRestriction(type, [base: base])
	restriction.schema = schema
	break;
	}

[rrayst]

Thanks for reporting the issue! We happily accept pull requests. :)