Fixed bug related to memory release in PNG image loader. Thanks elephoenix for it.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code@4913 dfc29bdd-3216-0410-991c-e03cc46cb475
- Revert last commit.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code@4914 dfc29bdd-3216-0410-991c-e03cc46cb475
Fixed bug related to memory release in PNG image loader. Thanks elephoenix for it.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code@4915 dfc29bdd-3216-0410-991c-e03cc46cb475