Number field icon missing

Number field icon missing front-end despite its back-end selection : viewbox is empty, only <path></path> in the source code.

<div style="margin-bottom: 5px;" class=" rnField_19 rnnumber rednaoWooField ">
<div class="rednaoControl"><div class="rnTextFieldInput ">
...
<div class="RNIconOrImage" style="width: 100%; display: flex; align-items: center; justify-content: center; height: 100%; color: rgb(191, 191, 191); font-size: 18px;">
<svg fill="currentColor" style="height: 1em;" viewBox=""><path></path></svg>
</div>
</div>
...
</div>