Add placeholder to workaround javadoc bug where it crashes attempting to find @javax.annotation.Nullable which is indirectly referenced from various Guava classes on the classpath

doclava/api/nullable.zip

diff --git a/doclava/api/nullable.zip b/doclava/api/nullable.zip
new file mode 100644
index 0000000..9b17e49
--- /dev/null
+++ b/doclava/api/nullable.zip
Binary files differ

pom.xml

diff --git a/pom.xml b/pom.xml
index 961e277..ea99999 100644
--- a/pom.xml
+++ b/pom.xml
@@ -278,9 +278,9 @@
             </docletArtifact>
             <doclet>com.google.doclava.Doclava</doclet>
             <!--
-             | bootclasspath required by Sun's JVM
+             | bootclasspath required by Sun's JVM, plus @Nullable placeholder to workaround javadoc bug
             -->
-            <bootclasspath>${sun.boot.class.path}</bootclasspath>
+            <bootclasspath>${sun.boot.class.path}:${basedir}/../doclava/api/nullable.zip</bootclasspath>
             <excludePackageNames>*.internal,org.codehaus.*</excludePackageNames>
             <additionalparam>
               -quiet