private WhiteSpace lastWhiteSpace() {
		if (symbols.size() == 0) {
			return null;
		}
		AssemblySymbol last = symbols.get(symbols.size() - 1);
		if (last instanceof WhiteSpace) {
			return (WhiteSpace) last;
		}
		return null;
	}
Add a syntactic terminal element, but considering that commas contained within may be
followed by optional whitespace

@param str the expected terminal
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/app/plugin/assembler/sleigh/grammars/AssemblySentential.java