- Initialize some variables in FModelVertex::Set

- Fix wrong normal vector in the FModelVertexBuffer constructor

This fixes models having strange flickering when the model animation frame changes

src/common/rendering/i_modelvertexbuffer.h

@@ -17,6 +17,8 @@ struct FModelVertex
 		z = zz;
 		u = uu;
 		v = vv;
+		lu = 0.0f;
+		lv = 0.0f;
 		lindex = -1.0f;
 	}