guard against variable not existing if vignette does not get compiled

Author: mountainMath

vignettes/partial_table_data_download.Rmd

@@ -48,7 +48,7 @@ bp_template_filtered <- bp_template %>%
 bp_template_filtered
 ```
 
-This leaves us with `r nrow(bp_template_filtered)` coordinates from the table. To get data for just this subset of the table we feed that into the `get_cansim_data_for_table_coord_periods` function. By default this will get the data for all available times, we could narrow it down to the latest $n$ periods using the `periods` argument, but here we want to get all available data. 
+This leaves us with `r if (exists("bp_template_filtered")) nrow(bp_template_filtered) else 96` coordinates from the table. To get data for just this subset of the table we feed that into the `get_cansim_data_for_table_coord_periods` function. By default this will get the data for all available times, we could narrow it down to the latest $n$ periods using the `periods` argument, but here we want to get all available data. 
 
 ```{r}
 bp_data <- get_cansim_data_for_table_coord_periods(bp_template_filtered)