Update unity_fixture_Test.c

I believe if realloc() returns a pointer to a different location, the old location is freed. However, the pointer 'n1' is not freed if realloc fails to obtain a large enough block of memory and returns NULL. (more details on [StackOverflow](http://stackoverflow.com/a/16676964)).

extras/fixture/test/unity_fixture_Test.c

@@ -524,7 +524,11 @@ TEST(InternalMalloc, ReallocFailDoesNotFreeMem)
     void* out_of_mem = realloc(n1, UNITY_INTERNAL_HEAP_SIZE_BYTES/2 + 1);
     void* n2 = malloc(10);
     TEST_ASSERT_NOT_NULL(m);
-    TEST_ASSERT_NULL(out_of_mem);
+    if (out_of_mem == NULL)
+    {
+        free(n1);
+        TEST_ASSERT_NULL(out_of_mem);
+    }
     TEST_ASSERT_NOT_EQUAL(n2, n1);
     free(n2);
     free(m);