Fix issue 50: potential segfault when commiting to a file
Fix issue 50: potential segfault when commiting to a file

When the roxml_commit_changes function could not open the destination file
the FILE *fout pointer was not tested leading to a segfault.

sartura/libroxml,gergap/libroxml,sartura/libroxml,gergap/libroxml,gergap/libroxml,mahmudur85/libroxml,mahmudur85/libroxml,gergap/libroxml,sartura/libroxml,gergap/libroxml,sartura/libroxml,mahmudur85/libroxml,mahmudur85/libroxml,sartura/libroxml,mahmudur85/libroxml