Serialization: Don't fail out of loadNamedMembers()

This cleanup exposed a problem with deserialization recovery and
property wrappers. If deserializing a property backed by a wrapper
failed, the lazy member lookup would fail, but subsequently a
loadAllMembers() call would still load the property.

This behavior is actually incorrect, because silently dropping a
stored property of a @frozen struct can result in miscompiles.
I've filed rdar://59403542 and rdar://59403617 to track fixing this.

In the meantime, I've tweaked the logic a bit to preserve the old
behavior.

lib/Serialization/ModuleFile.cpp

@@ -2399,7 +2399,7 @@ ModuleFile::loadNamedMembers(const IterableDeclContext *IDC, DeclBaseName N,
         fatalIfUnexpected(DeclMemberTablesCursor.advance());
     if (entry.Kind != llvm::BitstreamEntry::Record) {
       fatal();
-      return None;
+      return results;
     }
     SmallVector<uint64_t, 64> scratch;
     StringRef blobData;
@@ -2424,10 +2424,6 @@ ModuleFile::loadNamedMembers(const IterableDeclContext *IDC, DeclBaseName N,
         if (!getContext().LangOpts.EnableDeserializationRecovery)
           fatal(mem.takeError());
         consumeError(mem.takeError());
-
-        // Treat this as a cache-miss to the caller and let them attempt
-        // to refill through the normal loadAllMembers() path.
-        return None;
       }
     }
   }