hc-helper: Mute notes: "no visible binding for global variable:"

Change-Id: I2a12099bc88b93752a89e27a1330d1e8b1c822fa
diff --git a/R/highcharter-helper.R b/R/highcharter-helper.R
index b33689a..981d4d7 100644
--- a/R/highcharter-helper.R
+++ b/R/highcharter-helper.R
@@ -92,6 +92,9 @@
     hc_add_series_korap_frequencies(df, as.alternatives)
 }
 
+## Mute notes: "no visible binding for global variable:"
+globalVariables(c("value", "query", "condition", "vc"))
+
 hc_add_series_korap_frequencies <- function(hc, df, as.alternatives = F) {
   index <- 0
   for(q in unique(df$condition)) {