derekovecs: cutoff cannot be larger than number of words in vocabulary

Fixes segmentation fault with CoRoLa.
TODO: cut-off should be frequency based rather than rank based.
diff --git a/w2v-server.pl b/w2v-server.pl
index 26bea4b..e04f212 100755
--- a/w2v-server.pl
+++ b/w2v-server.pl
@@ -714,7 +714,7 @@
 
   if(N>MAX_NEIGHBOURS) N=MAX_NEIGHBOURS;
 	
-  if(cutoff < 1)
+  if(cutoff < 1 || cutoff > words)
     cutoff=words;
 
   wl = getTargetWords(st1, search_backw);