Fix findbugs warning

git-svn-id: https://svn.apache.org/repos/asf/jmeter/trunk@1756226 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/test/src/org/apache/jmeter/monitor/model/benchmark/ParseBenchmark.java b/test/src/org/apache/jmeter/monitor/model/benchmark/ParseBenchmark.java
index b1cf59e..aa76d8b 100644
--- a/test/src/org/apache/jmeter/monitor/model/benchmark/ParseBenchmark.java
+++ b/test/src/org/apache/jmeter/monitor/model/benchmark/ParseBenchmark.java
@@ -43,6 +43,9 @@
             if (args[2] != null) {
                 loops = Integer.parseInt(args[2]);
             }
+            if(file == null) {
+                throw new IllegalArgumentException("file is null");
+            }
             java.io.File infile = new java.io.File(file);
             java.io.FileInputStream fis = null;
             java.io.InputStreamReader isr = null;