Add asserts to Signal iOS .pch.

Signal/Signal-Prefix.pch

@@ -16,6 +16,7 @@
     #endif
 
     #import "iOSVersions.h"
+    #import "Asserts.h"
 
     #define SignalAlertView(title,msg) [[[UIAlertView alloc] initWithTitle:title message:msg delegate:nil cancelButtonTitle:NSLocalizedString(@"OK", @"") otherButtonTitles:nil, nil] show]
     #define SignalReportError [Pastelog reportErrorAndSubmitLogsWithAlertTitle:NSLocalizedString(@"ERROR_WAS_DETECTED_TITLE", @"") alertBody:NSLocalizedString(@"ERROR_WAS_DETECTED_SUBMIT", @"")];