[MASSEMBLY-847] attachmentClassifier shouldn't throw exception

**[David Hoffer](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=dahoffer)** opened **[MASSEMBLY-847](https://issues.apache.org/jira/browse/MASSEMBLY-847?redirect=false)** and commented

We want to use this plugin to generate a zip of all the javadoc binaries in the reactor so we set attachmentClassifier to javadocs. This would work perfect except it throws an exception every time it can't find a javadoc artifact. There are lots of modules, ears, wars, pom/resource type modules that generally do not have any javadocs. This means we have to add an exclude item for each one of them. This has become unmanageable as one has to remember to add to the exclude list every time a new module like this is created.

This plugin should be changed so that it does not throw if some are missing. If this behavior needs to be configurable that is fine.

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No further details from [MASSEMBLY-847](https://issues.apache.org/jira/browse/MASSEMBLY-847?redirect=false)

Start by locating the plugin logic that handles attachmentClassifier and reproduce the failure in a reactor containing modules without javadoc artifacts, such as ears, wars, poms, or resource modules. Done means missing javadoc artifacts no longer cause an exception and the requested javadoc archive can still be generated without per-module exclusions.

Written by the indexing model from the issue text.