fix category delete

src/main/kotlin/space/luminic/budgerapp/services/CategoryService.kt

@@ -3,6 +3,7 @@ package space.luminic.budgerapp.services
 
 import kotlinx.coroutines.reactive.awaitFirstOrNull
 import kotlinx.coroutines.reactive.awaitSingle
+import kotlinx.coroutines.reactor.awaitSingleOrNull
 import org.bson.Document
 import org.bson.types.ObjectId
 import org.slf4j.LoggerFactory
@@ -135,22 +136,26 @@ class CategoryService(
     suspend fun deleteCategory(space: Space, categoryId: String) {
         findCategory(space, categoryId)
         val transactions = financialService.getTransactions(space.id!!, categoryId = categoryId).awaitSingle()
-        val otherCategory = try {
-            findCategory(space, name = "Другое")
-        } catch (nfe: NotFoundException) {
-            categoryRepo.save(
-                Category(
-                    space = space,
-                    type = CategoryType("EXPENSE", "Траты"),
-                    name = "Другое",
-                    description = "Категория для других трат",
-                    icon = "🚮"
-                )
-            ).awaitSingle()
-        }
-        transactions.map { transaction ->
-            transaction.category = otherCategory
-            financialService.editTransaction(transaction)
+        if (transactions.isNotEmpty()) {
+            val otherCategory = try {
+                findCategory(space, name = "Другое")
+            } catch (nfe: NotFoundException) {
+                categoryRepo.save(
+                    Category(
+                        space = space,
+                        type = CategoryType("EXPENSE", "Траты"),
+                        name = "Другое",
+                        description = "Категория для других трат",
+                        icon = "🚮"
+                    )
+                ).awaitSingle()
+            }
+
+
+            transactions.map { transaction ->
+                transaction.category = otherCategory
+                financialService.editTransaction(transaction)
+            }
         }
         val budgets = financialService.findProjectedBudgets(
             ObjectId(space.id),
@@ -171,7 +176,7 @@ class CategoryService(
             budget.categories.removeIf { it.category.id == categoryId }
             budgetRepo.save(budget)
         }
-        categoryRepo.deleteById(categoryId).awaitSingle()
+        categoryRepo.deleteById(categoryId).awaitSingleOrNull()
     }
 
 }