writeScriptableOutput appends literal 'null' string for null classifier

[elharo]

AbstractAnalyzeMojo.writeScriptableOutput() at line 550:

buf.append(scriptableFlag)
    .append(":")
    .append(pomFile)
    .append(":")
    .append(artifact.getDependencyConflictId())
    .append(":")
    .append(artifact.getClassifier())    // appends "null" string
    .append(":")
    .append(artifact.getBaseVersion())
    .append(":")
    .append(artifact.getScope())
    .append(System.lineSeparator());

artifact.getClassifier() returns null when no classifier is set. StringBuilder.append(null) appends the literal string "null" instead of an empty string. For dependencies without a classifier, the output contains ...:null:... instead of ...::..., which breaks script consumption of the output.

Note that writeDependencyXML() (line 515) correctly handles null classifier with an explicit null check before appending.