Get rid of empty sequence warning in CA

Change-Id: I39d239f1a49871e975b9f60db434c68703cd84fd
diff --git a/R/collocationAnalysis.R b/R/collocationAnalysis.R
index d2ad284..0bcd691 100644
--- a/R/collocationAnalysis.R
+++ b/R/collocationAnalysis.R
@@ -259,7 +259,7 @@
       ))
     }
     log_info(verbose, paste("Joining", nrow(matches), "kwics\n"))
-    for (i in 1:nrow(matches)) {
+    for (i in seq_len(nrow(matches))) {
       oldTable <- matches2FreqTable(
         matches,
         i,