Compute dissimilarity matrix in R

Question

I wanted to compute a dissimilary matrix IN R by using the following code.

a <- A[,-c(2,3,4)]
b <- a[-c(201:321), ]
b <- unlist(b)

library(vegan)
PD.dist <- vegdist(b, method = "jaccard", binary = TRUE)
Pd.dist

The software R put the following answer

PD.dist <- vegdist(b, method = "jaccard", binary = TRUE)
Warning messages:
1: In vegdist(b, method = "jaccard", binary = TRUE) :
  you have empty rows: their dissimilarities may be meaningless in method “jaccard”
2: In vegdist(b, method = "jaccard", binary = TRUE) :
  missing values in results

I went in my dataframe to search if i had empty rows by it was not the case What can I do?