Do not allow repeated nodes in collocation analysis

Change-Id: I19e5db6dc40ae7a25f9eddff4325a71846dcaf6f
diff --git a/R/collocationAnalysis.R b/R/collocationAnalysis.R
index bf962f6..eb691f8 100644
--- a/R/collocationAnalysis.R
+++ b/R/collocationAnalysis.R
@@ -76,7 +76,7 @@
                    ignoreCollocateCase = FALSE,
                    withinSpan = ifelse(exactFrequencies, "base/s=s", ""),
                    exactFrequencies = TRUE,
-                   stopwords = RKorAPClient::synsemanticStopwords(),
+                   stopwords = append(RKorAPClient::synsemanticStopwords(), node),
                    seed = 7,
                    expand = length(vc) != length(node),
                    ...) {