Fix: Support non-empty values

Dropdown does not show correct styling if using a falsey value such as `false` or `0`.

components/lib/dropdown/Dropdown.vue

@@ -950,7 +950,7 @@ export default {
                     'p-disabled': this.disabled,
                     'p-dropdown-clearable': this.showClear && !this.disabled,
                     'p-focus': this.focused,
-                    'p-inputwrapper-filled': this.modelValue,
+                    'p-inputwrapper-filled': this.hasSelectedOption,
                     'p-inputwrapper-focus': this.focused || this.overlayVisible,
                     'p-overlay-open': this.overlayVisible
                 }