fix clear DB

iOSClient/Settings/CCAdvanced.m

@@ -201,6 +201,7 @@
             
             [[NCManageDatabase sharedInstance] clearTable:[tableActivity class] account:appDelegate.activeAccount];
             [[NCManageDatabase sharedInstance] clearTable:[tableActivitySubjectRich class] account:appDelegate.activeAccount];
+            [[NCManageDatabase sharedInstance] clearTable:[tableActivityPreview class] account:appDelegate.activeAccount];
             [[NCManageDatabase sharedInstance] clearTable:[tableCapabilities class] account:appDelegate.activeAccount];
             [[NCManageDatabase sharedInstance] clearTable:[tableDirectory class] account:appDelegate.activeAccount];
             [[NCManageDatabase sharedInstance] clearTable:[tableE2eEncryption class] account:appDelegate.activeAccount];