Fixed IOStream reporting a file size of 0 for files that have been written, but not yet been flushed to disk.

test/unit/utDefaultIOStream.cpp

@@ -69,6 +69,11 @@ TEST_F( utDefaultIOStream, FileSizeTest ) {
         auto vflush = std::fflush( fs );
         ASSERT_EQ(vflush, 0);
 
+		std::fclose(fs);
+		fs = std::fopen(fpath, "r");
+
+		ASSERT_NE(nullptr, fs);
+
         TestDefaultIOStream myStream( fs, fpath);
         size_t size = myStream.FileSize();
         EXPECT_EQ( size, dataSize);