correct check for tmap in sids_models

Author: rsbivand

Diff for: vignettes/sids_models.Rmd

@@ -63,8 +63,8 @@ nc$both <- factor(paste(nc$L_id, nc$M_id, sep=":"))
 ```{r, echo=FALSE}
 is_tmap <- FALSE
 if (require(tmap, quietly=TRUE)) is_tmap <- TRUE
-is_tmap
-tmap4 <- packageVersion("tmap") >= "3.99"
+tmap4 <- FALSE
+if(is_tmap) tmap4 <- packageVersion("tmap") >= "3.99"
 ```
 
 We will now examine the data set reproduced from Cressie and