Merge branch 'bug/1951-improve-handling-of-missing-schema-map' of https://github.com/icikle/swagger-parser into bug/1951-improve-handling-of-missing-schema-map

* 'bug/1951-improve-handling-of-missing-schema-map' of https://github.com/icikle/swagger-parser:
  Prevent NPE from missing schema on Component.  Improve exception handling.

# Conflicts:
#	modules/swagger-parser-v3/src/test/java/io/swagger/v3/parser/test/OAIDeserializationTest.java

Author: ian-kettle-fm