Fix sonar warnings.

Author: javadev

src/main/java/com/github/underscore/lodash/U.java

@@ -955,11 +955,18 @@ public static <T extends Number> Double average(final Iterable<T> iterable) {
 
     public static <E, F extends  Number> Double average(final Iterable<E> iterable, final Function<E, F> func) {
         F sum = sum(iterable, func);
+        if (sum == null) {
+            return null;
+        }
         return sum.doubleValue() / size(iterable);
     }
 
     public static <N extends Number> Double average(N[] array) {
-        return sum(array).doubleValue() / array.length;
+        N sum = sum(array);
+        if (sum == null) {
+            return null;
+        }
+        return sum.doubleValue() / array.length;
     }
 
     public static Double average(java.math.BigDecimal first, java.math.BigDecimal second) {

src/test/java/com/github/underscore/lodash/MathTest.java

@@ -50,6 +50,12 @@ public Byte apply(final Byte item) {
             }
         });
         assertEquals("4.0", resultFunc.toString());
+        final Double resultFunc2 = U.average(asList((Byte) null), new Function<Byte, Byte>() {
+            public Byte apply(final Byte item) {
+                return item;
+            }
+        });
+        assertNull(resultFunc2);
         assertEquals("2.0", result.toString());
         final Double result2 = U.average(asList((double) 1, (double) 2, (double) 3));
         assertEquals("2.0", result2.toString());
@@ -133,6 +139,10 @@ public Byte apply(final Byte item) {
         assertNull(result40);
         final Double result41 = U.average(Long.valueOf(2), Long.valueOf(4));
         assertEquals("3.0", result41.toString());
+        final Double result42 = U.average(Long.valueOf(2), Long.valueOf(4));
+        assertEquals("3.0", result41.toString());
+        final Double result43 = U.average(new Integer[] {(Integer) null});
+        assertNull(result43);
     }
 
 /*