improved error reporting in Material.get_data()
improved error reporting in Material.get_data()

rc/sfepy,lokik/sfepy,RexFuzzle/sfepy,rc/sfepy,RexFuzzle/sfepy,RexFuzzle/sfepy,olivierverdier/sfepy,vlukes/sfepy,BubuLK/sfepy,BubuLK/sfepy,vlukes/sfepy,lokik/sfepy,sfepy/sfepy,sfepy/sfepy,vlukes/sfepy,sfepy/sfepy,lokik/sfepy,olivierverdier/sfepy,BubuLK/sfepy,olivierverdier/sfepy,rc/sfepy,RexFuzzle/sfepy,lokik/sfepy