SAMOA-58: forgot to initialize support array
diff --git a/samoa-api/src/main/java/org/apache/samoa/evaluation/F1ClassificationPerformanceEvaluator.java b/samoa-api/src/main/java/org/apache/samoa/evaluation/F1ClassificationPerformanceEvaluator.java
index 3046360..726f487 100644
--- a/samoa-api/src/main/java/org/apache/samoa/evaluation/F1ClassificationPerformanceEvaluator.java
+++ b/samoa-api/src/main/java/org/apache/samoa/evaluation/F1ClassificationPerformanceEvaluator.java
@@ -48,6 +48,7 @@
 
     public void reset(int numClasses) {
         this.numClasses = numClasses;
+        this.support = new long[numClasses];
         this.truePos = new long[numClasses];
         this.falsePos = new long[numClasses];
         this.trueNeg = new long[numClasses];