新增错误处理

新增对发布内容的输入校验，并在输入不合法时弹出提示信息。

app/src/main/java/com/aiosman/riderpro/ui/post/NewPostViewModel.kt

@@ -48,6 +48,12 @@ object NewPostViewModel : ViewModel() {
         return tempFile
     }
 
+    fun validateMoment(): String? {
+        if (imageUriList.isEmpty()) {
+            return "Please select at least one image"
+        }
+        return null
+    }
     suspend fun createMoment(context: Context, onUploadProgress: (Float) -> Unit) {
         val uploadImageList = emptyList<UploadImage>().toMutableList()
         var index = 0