Return -1 if MemoryUsage is null

Author: jinhyukify

hbase-server/src/main/java/org/apache/hadoop/hbase/io/util/MemorySizeUtil.java

@@ -243,7 +243,10 @@ public static long getOnHeapCacheSize(final Configuration conf) {
     }
 
     final MemoryUsage usage = safeGetHeapMemoryUsage();
-    final long heapMax = usage != null ? usage.getMax() : -1;
+    if (usage == null) {
+      return -1;
+    }
+    final long heapMax = usage.getMax();
     float onHeapCacheFixedSize =
       (float) conf.getLong(HConstants.HFILE_ONHEAP_BLOCK_CACHE_FIXED_SIZE_KEY,
         HConstants.HFILE_ONHEAP_BLOCK_CACHE_FIXED_SIZE_DEFAULT) / heapMax;