private boolean isValidChars(String string) {
		char replaceChar = '\ufffd';
		for (int i = 0; i < string.length(); ++i) {
			char c = string.charAt(i);
			if (c == replaceChar) {
				return false;
			}
		}
		return true;
	}
Return true if there are no "replacement" characters in the string
@param string is the string to test
@return true if no replacements
Ghidra/Features/Decompiler/src/main/java/ghidra/app/decompiler/DecompileCallback.java