Fixed bug related to clean up of text fonts.

src/osgText/Text.cpp

@@ -1639,13 +1639,10 @@ void Text::accept(osg::PrimitiveFunctor& pf) const
     
 }
 
-/** If State is non-zero, this function releases OpenGL objects for
-  * the specified graphics context. Otherwise, releases OpenGL objexts
-  * for all graphics contexts. */
 void Text::releaseGLObjects(osg::State* state) const
 {
     Drawable::releaseGLObjects(state);
-    if (_font.valid()) _font->releaseGLObjects(state);
+    getActiveFont()->releaseGLObjects(state);
 }