Revert "Revert 42b1104 (#1499)"

This reverts commit c1f3271a372e72e5c3fc101631b43a46eb7250e2.

src/renderer_gl.cpp

@@ -4487,7 +4487,7 @@ BX_TRACE("%d, %d, %d, %s", _array, _srgb, _mipAutogen, getName(_format) );
 					GL_CHECK(glVertexAttribDivisor(loc, 0) );
 
 					uint32_t baseVertex = _baseVertex*_vertexDecl.m_stride + _vertexDecl.m_offset[attr];
-					if (NULL != glVertexAttribIPointer
+					if ( (BX_ENABLED(BGFX_CONFIG_RENDERER_OPENGL >= 30) ||  BX_ENABLED(BGFX_CONFIG_RENDERER_OPENGLES >= 31) )
 					&& (AttribType::Uint8 == type || AttribType::Int16 == type)
 					&&  !normalized)
 					{