ResolverCache calls OpenAPIDeserializer.getSchema with null ParseResult

I get:

Exception while reading:
java.lang.NullPointerException
at io.swagger.v3.parser.util.OpenAPIDeserializer.getArray (OpenAPIDeserializer.java:1299)
at io.swagger.v3.parser.util.OpenAPIDeserializer.getSchema (OpenAPIDeserializer.java:2152)
at io.swagger.v3.parser.util.OpenAPIDeserializer.getSchema (OpenAPIDeserializer.java:2214)
at io.swagger.v3.parser.ResolverCache.loadRef (ResolverCache.java:148)
at io.swagger.v3.parser.processors.ExternalRefProcessor.processRefToExternalSchema (ExternalRefProcessor.java:52)
at io.swagger.v3.parser.processors.ExternalRefProcessor.processRefToExternalSchema (ExternalRefProcessor.java:108)
at io.swagger.v3.parser.processors.SchemaProcessor.processReferenceSchema (SchemaProcessor.java:202)
at io.swagger.v3.parser.processors.SchemaProcessor.processComposedSchema (SchemaProcessor.java:118)
at io.swagger.v3.parser.processors.SchemaProcessor.processSchemaType (SchemaProcessor.java:50)
at io.swagger.v3.parser.processors.SchemaProcessor.processSchema (SchemaProcessor.java:39)
at io.swagger.v3.parser.processors.RequestBodyProcessor.processRequestBody (RequestBodyProcessor.java:44)
at io.swagger.v3.parser.processors.OperationProcessor.processOperation (OperationProcessor.java:45)
at io.swagger.v3.parser.processors.PathsProcessor.processPaths (PathsProcessor.java:84)
at io.swagger.v3.parser.OpenAPIResolver.resolve (OpenAPIResolver.java:49)
at io.swagger.v3.parser.OpenAPIV3Parser.readLocation (OpenAPIV3Parser.java:53)
at io.swagger.v3.parser.OpenAPIV3Parser.read (OpenAPIV3Parser.java:90)
at io.swagger.v3.parser.OpenAPIV3Parser.read (OpenAPIV3Parser.java:78)

This is caused by a null reference being passed for ParseResult. So I don't know where the parse error is. Indeed it's unclear how it would pass a non-null ParseResult, as it's a protected member of OpenAPIDeserializer. I've had to hack the source code to work out what my syntax error is.

Start at ResolverCache.loadRef and follow the reported calls into OpenAPIDeserializer.getSchema and getArray, focusing on how ParseResult reaches the deserializer. Reproduce the reported parsing failure and make the parser expose the underlying syntax error instead of failing with a NullPointerException.