OpenAPIDeserializer produces NPE when a path references an undeclared path parameter

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The OpenAPIDeserializer runs into a NPE and, as a consequence, produces a diagnostic message with content "null", when a path references a path parameter that is not declared in the respective operation.

How to reproduce:

1. Store this file as input.json

input.json.gz
.

2. Store this file as ParseOpenAPI3File.java.

ParseOpenAPI3File.java.gz

Compile it with a classpath that contains
slf4j-api-1.5.8.jar
slf4j-jdk14-1.5.8.jar
jackson-core-2.11.0.jar
jackson-dataformat-yaml-2.11.0.jar
jackson-databind-2.11.0.jar
jackson-annotations-2.11.0.jar
jackson-datatype-jsr310-2.11.0.jar
commons-io-1.4.jar
commons-lang3-3.1.jar
swagger-models-2.1.3.jar
swagger-core-2.1.3.jar
swagger-parser-v3-2.0.20.jar
swagger-parser-core-2.0.20.jar
snakeyaml.jar

3. Run it with one argument, namely the absolute file name from step 1.

Expected output:

Messages from OpenAPIV3Parser:
attribute paths.'/restTest/arraytypes/complexArrayEcho/{value}'. Declared path parameter value needs to be defined as a path parameter in path or operation level
attribute paths.'/restTest/arraytypes/complexArrayEcho/{value}'. Declared path parameter value needs to be defined as a path parameter in path or operation level

Actual output:

Messages from OpenAPIV3Parser:
null

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The following patch fixes it:
1402-fix.diff.gz

[gracekarina]

thanks @brhaible