Don't pass null to Function.apply

This is a workaround for a DDC bug.  Will fix that now, but it'll take a bit to roll in.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=148518715
diff --git a/lib/message_lookup_by_library.dart b/lib/message_lookup_by_library.dart
index d596c03..7ef2a8d 100644
--- a/lib/message_lookup_by_library.dart
+++ b/lib/message_lookup_by_library.dart
@@ -50,8 +50,7 @@
     if (messages == null) {
       return ifAbsent(message_str, args);
     }
-    return messages.lookupMessage(
-        message_str, locale, name, args, meaning,
+    return messages.lookupMessage(message_str, locale, name, args, meaning,
         ifAbsent: ifAbsent);
   }
 
@@ -121,6 +120,7 @@
     if (notFound) {
       return ifAbsent == null ? message_str : ifAbsent(message_str, args);
     } else {
+      args = args ?? [];
       return Function.apply(function, args);
     }
   }