Check if given classname exists in GType system. Refs gh-120
Check if given classname exists in GType system. Refs gh-120

midgardproject/midgard-core,midgardproject/midgard-core,piotras/midgard-core,piotras/midgard-core,piotras/midgard-core,piotras/midgard-core,midgardproject/midgard-core,midgardproject/midgard-core