IPS-168 Doc all asserts, make sure release builds do the right thing as well

src/PEPBlockBasedTransport.m

@@ -130,8 +130,7 @@
         return;
     }
 
-    // Message IDs must be unique, or we'll have problems. Let's find out rather sooner,
-    // during development, than later.
+    // Make sure there are not already callbacks existing for the message ID.
     PEPTransportStatusCallbacks *existingCallbacks = [self.messageCallbacks objectForKey:messageID];
     NSAssert(existingCallbacks == nil,
              @"Sending a message with a message ID that is currently in the process of sending is not supported");

src/TransportDelegates/PEPBlockBasedTransport+IncomingMessageDelegate.m

@@ -19,9 +19,8 @@
                                                 transportStatusCode:&statusCodeFromUnderlyingTransport
                                                               error:&error];
     if (message == nil) {
-        // Weird case, but nothing to relay to the delegate.
-        // For now, assume implementation error.
-        NSAssert(NO, @"Underlying transport signaled new message, but could not read it");
+        // Weird case, but nothing to relay to the delegate, so ignore.
+        NSAssert(NO, @"Underlying transport signaled new message, but there was none");
     } else {
         [self.transportDelegate signalIncomingMessage:message
                                           transportID:transportID

src/TransportDelegates/PEPBlockBasedTransport+SendToResultDelegate.m

@@ -41,8 +41,12 @@
                                statusCode:(PEPTransportStatusCode)statusCode {
     PEPTransportStatusCallbacks *callbacks = [self findAndRemoveCallbacksForMessageID:messageID];
 
-    // That would look like a developer error.
+    // If we don't find the matching callbacks for this message ID,
+    // there's nothing we can do.
     NSAssert(callbacks != nil, @"Got called with message send result, but no callback");
+    if (callbacks == nil) {
+        return;
+    }
 
     if ([PEPTransportStatusCodeUtil isErrorStatusCode:statusCode] ||
         [PEPTransportStatusCodeUtil isCriticalErrorStatusCode:statusCode]) {