Failed to run on Mobile Safari

[hideya]

Execution fails with the following error at the start up (during the warm-up) and when clicking "Guess" button.

A TF.js demo, Emoji Scavenger Hunt, that uses similar features, runs fine on Mobile Safari. So, there should be a way to fix it.

iOS version tested is 11.3 and TF.js is of version_core: "0.9.1".

[Error] Error: Can't squeeze axis 1 since its dim '2' is not 1
    squeezeShape (util.js:248)
    squeeze (array_ops.js:348)
    executeOp (transformation_executor.js:16)
    (anonymous function) (graph_executor.js:139)
    reduce
    (anonymous function) (graph_executor.js:137)
    tidy (tracking.js:36)
    execute (graph_executor.js:135)
    execute (frozen_model.js:161)
    (anonymous function) (index.js:46)
    tidy (tracking.js:36)
    (anonymous function) (index.js:44:84)

Note that the following error is also shown during the warmup (only once).
Although this freezes the execution for a while, the app resumes the execution successfully:

[Error] WebGL: INVALID_ENUM: readPixels: invalid type
    readPixels
    isFloatTextureReadPixelsEnabled (environment.js:106)
    get (environment.js:157)
    getTextureInternalFormat (gpgpu_util.js:90)
    createAndConfigureTexture (gpgpu_util.js:123)
    acquireTexture (texture_manager.js:32)
    uploadToGPU (backend_webgl.js:833)
    getTexture (backend_webgl.js:293)
    fromPixels (backend_webgl.js:137)
    tidy (tracking.js:36)
    (anonymous function) (webcam.js:51:92)
    tidy (tracking.js:36)
    (anonymous function) (index.js:45)
    tidy (tracking.js:36)
    (anonymous function) (index.js:44:84)

The above error is also seen on Safari, whereas the one failing on squeezeShape happens only on Mobile Safari.