shiny demo: fix query split

Change-Id: I519db8f6201e3c71ca71d609d349c09b83d75165
diff --git a/inst/shiny-apps/frequency_curves/server.R b/inst/shiny-apps/frequency_curves/server.R
index a2e1477..de740bf 100644
--- a/inst/shiny-apps/frequency_curves/server.R
+++ b/inst/shiny-apps/frequency_curves/server.R
@@ -56,7 +56,7 @@
 generateHighchart <- function(wordParam, from=2005, to=2020) {
   years <<- c(from:to)
   if (wordParam != "") {
-    query <<- str_split(wordParam, " *, *", simplify = TRUE)
+    query <<- strsplit(wordParam, " *, *")
     withProgress(message = 'Berechnung läuft: ', value = 0, {
       hc <- plotHighchart(query, vc , years)
     })