mvn clean site results in empty markdown files

[JakeSCahill]

Bug description

After running mvn clean site the resulting site directory contains empty markdown files for the API docs.

IRI version

1.8.4

Steps To Reproduce

1. mvn clean site
2. Go to site > apidocs

Expected behaviour

The markdown files should include documentation for the API endpoints

Actual behaviour

The markdown files are empty

Errors

[WARNING] Javadoc Warnings
[WARNING] javadoc: warning - The old Doclet and Taglet APIs in the packages
[WARNING] com.sun.javadoc, com.sun.tools.doclets and their implementations
[WARNING] are planned to be removed in a future JDK release. These
[WARNING] components have been superseded by the new APIs in jdk.javadoc.doclet.
[WARNING] Users are strongly recommended to migrate to the new APIs.
[WARNING] C:\Users\Jake Cahill\Documents\contribution-guidelines\iri\src\main\java\com\iota\iri\IXI.java:31: error: package com.sun.jmx.mbeanserver is not visible
[WARNING] import static com.sun.jmx.mbeanserver.Util.cast;
[WARNING] ^
[WARNING] (package com.sun.jmx.mbeanserver is declared in module java.management, which does not export it)
[WARNING] C:\Users\Jake Cahill\Documents\contribution-guidelines\iri\src\main\java\com\iota\iri\IXI.java:31: error: static import only from classes and interfaces
[WARNING] import static com.sun.jmx.mbeanserver.Util.cast;
[WARNING] ^
[WARNING] Feb 18, 2020 4:03:57 PM freemarker.log._JULLoggerFactory$JULLogger error
[WARNING] SEVERE: Error executing FreeMarker template
[WARNING] FreeMarker template error:
[WARNING] Java method "com.sun.tools.javadoc.main.ProgramElementDocImpl.containingClass()" threw an exception when invoked on com.sun.tools.javadoc.main.MethodDocImpl object "com.iota.iri.service.API.wereAddressesSpentFromStatement(java.util.List<java.lang.String>)"; see cause exception in the Java stack trace.
[WARNING]
[WARNING] ----
[WARNING] FTL stack trace ("~" means nesting-related):
[WARNING] - Failed at: ${subject.containingClass().qualified...  [in template "iri-template.ftl" at line 4, column 33]
[WARNING] ----