fix: validate asset edits before deleting the cached file (#6190)

Reject duplicate names and empty names or URLs before invalidating the existing asset cache. Previously a rejected save left the stored source unchanged but deleted its downloaded file.

Preserve the validation messages and their order, duplicate-name exclusion by asset ID, and successful-save behavior. Renames still invalidate the old filename before updating the asset record.

V2rayNG/app/src/main/java/com/v2ray/ang/ui/userasset/UserAssetUrlActivity.kt

@@ -81,6 +81,20 @@ class UserAssetUrlActivity : BaseComponentActivity() {
     }
 
     private fun saveServer(remarks: String, url: String): Boolean {
+        val assetList = MmkvManager.decodeAssetUrls()
+        if (assetList.any { it.assetUrl.remarks == remarks && it.guid != editAssetId }) {
+            toast(R.string.msg_remark_is_duplicate)
+            return false
+        }
+        if (TextUtils.isEmpty(remarks)) {
+            toast(R.string.sub_setting_remarks)
+            return false
+        }
+        if (TextUtils.isEmpty(url)) {
+            toast(R.string.title_url)
+            return false
+        }
+
         var assetItem = MmkvManager.decodeAsset(editAssetId)
         var assetId = editAssetId
         if (assetItem != null) {
@@ -100,20 +114,6 @@ class UserAssetUrlActivity : BaseComponentActivity() {
         assetItem.remarks = remarks
         assetItem.url = url
 
-        val assetList = MmkvManager.decodeAssetUrls()
-        if (assetList.any { it.assetUrl.remarks == assetItem.remarks && it.guid != assetId }) {
-            toast(R.string.msg_remark_is_duplicate)
-            return false
-        }
-        if (TextUtils.isEmpty(assetItem.remarks)) {
-            toast(R.string.sub_setting_remarks)
-            return false
-        }
-        if (TextUtils.isEmpty(assetItem.url)) {
-            toast(R.string.title_url)
-            return false
-        }
-
         MmkvManager.encodeAsset(assetId, assetItem)
         toastSuccess(R.string.toast_success)
         finish()