fix deleting directory

this used to corrupt the local state (password entities remained in DB
but files/dirs were removed from git and disk)

passKit/Helpers/AppError.swift

@@ -15,6 +15,7 @@ public enum AppError: Error, Equatable {
     case keyImport
     case readingFile(fileName: String)
     case passwordDuplicated
+    case cannotDeleteDirectory
     case gitReset
     case gitCommit
     case gitCreateSignature

passKit/Models/PasswordStore.swift

@@ -273,6 +273,10 @@ public class PasswordStore {
     }
 
     public func delete(passwordEntity: PasswordEntity) throws {
+        if passwordEntity.isDir {
+            throw AppError.cannotDeleteDirectory
+        }
+
         let deletedFileURL = passwordEntity.fileURL(in: storeURL)
         let deletedFilePath = passwordEntity.path
         try gitRm(path: passwordEntity.path)