Fix notifications sometimes getting deleted in group merging

Closes #156

Pachyderm/Sources/Pachyderm/Utilities/NotificationGroup.swift

@@ -97,13 +97,14 @@ public struct NotificationGroup: Identifiable, Hashable {
                 break
             }
             
-                    
             if canMerge(notification: firstGroupFromSecond.notifications.first!, into: lastGroup) {
                 merged[merged.count - 1].append(group: firstGroupFromSecond)
             } else if merged.count >= 2 {
                 let secondToLastGroup = merged[merged.count - 2]
                 if allowedTypes.contains(secondToLastGroup.kind), canMerge(notification: firstGroupFromSecond.notifications.first!, into: secondToLastGroup) {
                     merged[merged.count - 2].append(group: firstGroupFromSecond)
+                } else {
+                    merged.append(firstGroupFromSecond)
                 }
             } else {
                 merged.append(firstGroupFromSecond)

Pachyderm/Tests/PachydermTests/NotificationGroupTests.swift

@@ -148,9 +148,31 @@ class NotificationGroupTests: XCTestCase {
       "status": \(statusB)
     """.data(using: .utf8)!
     lazy var likeB = try! decoder.decode(Notification.self, from: likeBData)
-    lazy var mentionBData = """
+    lazy var likeB2Data = """
     {
       "id": "4",
+      "type": "favourite",
+      "created_at": "2019-11-23T07:29:18Z",
+      "account": {
+        "id": "2",
+        "username": "bar",
+        "acct": "bar",
+        "display_name": "bar",
+        "locked": false,
+        "created_at": "2019-11-02T01:01:01Z",
+        "followers_count": 0,
+        "following_count": 0,
+        "statuses_count": 0,
+        "note": "",
+        "url": "https://example.com/@bar",
+        "uri": "https://example.com/@bar",
+      },
+      "status": \(statusB)
+    """.data(using: .utf8)!
+    lazy var likeB2 = try! decoder.decode(Notification.self, from: likeB2Data)
+    lazy var mentionBData = """
+    {
+      "id": "5",
       "type": "mention",
       "created_at": "2019-11-23T07:29:18Z",
       "account": {
@@ -218,6 +240,17 @@ class NotificationGroupTests: XCTestCase {
             NotificationGroup(notifications: [likeA1, likeA2])!,
             NotificationGroup(notifications: [likeB])!,
         ])
+        
+        let group4 = NotificationGroup(notifications: [likeB2])!
+        let group5 = NotificationGroup(notifications: [mentionB])!
+        let merged3 = NotificationGroup.mergeGroups(first: [group1, group5, group2], second: [group4, group3], only: [.favourite])
+        print(merged3.count)
+        XCTAssertEqual(merged3, [
+            group1,
+            group5,
+            NotificationGroup(notifications: [likeB, likeB2]),
+            group3
+        ])
     }
     
     func testDontMergeWithUngroupableInBetween() {