Added back a missing type check

SessionMessagingKit/Sending & Receiving/Attachments/TSAttachmentPointer.m

@@ -169,8 +169,10 @@ NS_ASSUME_NONNULL_BEGIN
     // Legacy instances of TSAttachmentPointer apparently used the serverId as their
     // uniqueId.
     if (attachmentSchemaVersion < 2 && self.serverId == 0) {
-        // For legacy instances, try to parse the serverId from the uniqueId.
+        if ([self isDecimalNumberText:self.uniqueId]) {
-        self.serverId = (UInt64)[self.uniqueId integerValue];
+            // For legacy instances, try to parse the serverId from the uniqueId.
+            self.serverId = (UInt64)[self.uniqueId integerValue];
+        }
     }
 }