pass computeColor into shadow control, fix shadow switching types due to invalid shadow color

src/components/shadow_control/shadow_control.js

@@ -46,6 +46,7 @@ export default {
     'separateInset',
     'noPreview',
     'disabled',
+    'computeColor',
     'compact'
   ],
   emits: ['update:modelValue', 'subShadowSelected'],
@@ -107,6 +108,13 @@ export default {
     usingFallback () {
       return this.modelValue == null
     },
+    getFallback () {
+      if (typeof this.computeColor === 'function' && this.selected?.color) {
+        return this.computeColor(this.selected.color)
+      } else {
+        return this.currentFallback?.color
+      }
+    },
     style () {
       try {
         if (this.separateInset) {

src/components/shadow_control/shadow_control.vue

@@ -165,7 +165,7 @@
           :model-value="selected?.color"
           :disabled="disabled || !present"
           :label="$t('settings.style.common.color')"
-          :fallback="currentFallback?.color"
+          :fallback="getFallback"
           :show-optional-tickbox="false"
           name="shadow"
           @update:modelValue="e => updateProperty('color', e)"