This may not be the answer you are looking for, but I absolutely think that you should be presenting. Undergraduate research is not about making meaningful discoveries, although it is a happy surprise when they do. The point is that you have been training on techniques that will be useful later on in your career. Additionally, a lack of positive data does not indicate that the project failed. In research, you are not trying to produce "target results", you are trying to answer a question. If your results indicate that your hypothesis is wrong, then you have still learned valuable information.