Follow up on #1090 for overlay’s opacity

I missed that one and I fixed a bug in the meantime setting a correct label (vs. invisible placeholder for an input of type range).

I set a fallback on the datalist id in case no label is specified (which is probably not a good idea).

umap/static/umap/js/umap.forms.js

@@ -808,7 +808,7 @@ L.FormBuilder.Range = L.FormBuilder.Input.extend({
       'umap-field-datalist',
       this.getHelpTextParent()
     )
-    datalist.id = `range-${this.options.label}`
+    datalist.id = `range-${this.options.label || this.name}`
     this.input.setAttribute('list', datalist.id)
     var options = ''
     for (var i = this.options.min; i <= this.options.max; i += this.options.step) {

umap/static/umap/js/umap.js

@@ -1651,7 +1651,7 @@ L.U.Map.include({
       ],
       [
         'options.overlay.opacity',
-        { handler: 'Range', min: 0, max: 1, step: 'any', placeholder: L._('opacity') },
+        { handler: 'Range', min: 0, max: 1, step: 0.1, label: L._('Opacity') },
       ],
       ['options.overlay.tms', { handler: 'Switch', label: L._('TMS format') }],
     ]