GLES1: Fix behavior with incomplete mipmap textures GLES1 requires texturing to be disabled when a mipmap-enabled texture is incomplete. Bug: angleproject:3408 Change-Id: I2c3b0206282a71f9a54d77ecdf2c7e42c7175fe5 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3896212 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Yuxin Hu <yuxinhu@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>