Bug 53201 NPE when re-running newly generated javadoc.xml
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javadocexport/JavadocOptionsManager.java
if (fUse)
				toolArgs.add("-use"); 
			if (fVersion)
				toolArgs.add("-version"); 
			if (fAuthor)
				toolArgs.add("-author"); 
			if (fNonavbar)
				toolArgs.add("-nonavbar"); 
			if (fNoindex)
				toolArgs.add("-noindex"); 
			if (fNotree)
				toolArgs.add("-notree"); 
			if (fNodeprecated)
				toolArgs.add("-nodeprecated"); 
			if (fNoDeprecatedlist)
				toolArgs.add("-nodeprecatedlist"); 
			if (fSplitindex)
				toolArgs.add("-splitindex"); 
			if (fTitle.length() != 0) { 
				toolArgs.add("-doctitle"); 
				toolArgs.add(fTitle);
			}
			if (fStylesheet.length() != 0) { 
				toolArgs.add("-stylesheetfile"); 
				toolArgs.add(fStylesheet);
			}
			if (fAdditionalParams.length() + fVMParams.length() != 0) {
				ExecutionArguments tokens= new ExecutionArguments(fVMParams, fAdditionalParams); 
				String[] vmArgsArray= tokens.getVMArgumentsArray();