Avoid passing empty entity sets to ProtocolHelper

The methods there tend to throw Exceptions in such situations.

src/core/jobs/itemcreatejob.cpp

@@ -118,11 +118,16 @@ void ItemCreateJob::doStart()
         cmd.setAddedFlags(d->mItem.d_func()->mAddedFlags);
         cmd.setRemovedFlags(d->mItem.d_func()->mDeletedFlags);
     }
-    if (d->mItem.d_func()->mTagsOverwritten || !merge) {
+    if (!d->mItem.d_func()->mAddedTags.isEmpty() && (d->mItem.d_func()->mTagsOverwritten || !merge)) {
+
         cmd.setTags(ProtocolHelper::entitySetToScope(d->mItem.d_func()->mAddedTags));
     } else {
-        cmd.setAddedTags(ProtocolHelper::entitySetToScope(d->mItem.d_func()->mAddedTags));
-        cmd.setRemovedTags(ProtocolHelper::entitySetToScope(d->mItem.d_func()->mDeletedTags));
+        if (!d->mItem.d_func()->mAddedTags.isEmpty()) {
+            cmd.setAddedTags(ProtocolHelper::entitySetToScope(d->mItem.d_func()->mAddedTags));
+        }
+        if (!d->mItem.d_func()->mDeletedTags.isEmpty()) {
+            cmd.setRemovedTags(ProtocolHelper::entitySetToScope(d->mItem.d_func()->mDeletedTags));
+        }
     }
 
     cmd.setCollection(ProtocolHelper::entityToScope(d->mCollection));

src/core/jobs/itemfetchjob.cpp

@@ -171,8 +171,8 @@ void ItemFetchJob::doStart()
 
 
     try {
-        d->sendCommand(Protocol::FetchItemsCommand(
-            ProtocolHelper::entitySetToScope(d->mRequestedItems),
+        Scope itemScope(d->mRequestedItems.isEmpty() ? ImapSet::all() : ProtocolHelper::entitySetToScope(d->mRequestedItems));
+        d->sendCommand(Protocol::FetchItemsCommand(itemScope,
             ProtocolHelper::commandContextToProtocol(d->mCollection, d->mTag, d->mRequestedItems),
             ProtocolHelper::itemFetchScopeToProtocol(d->mFetchScope)));
     } catch (const Akonadi::Exception &e) {

src/core/protocolhelper_p.h

@@ -138,7 +138,7 @@ public:
         Container<T> objects(_objects);
 
         std::sort(objects.begin(), objects.end(), boost::bind(&T::id, _1) < boost::bind(&T::id, _2));
-        if (objects.first().isValid()) {
+        if (objects.at(0).isValid()) {
             QVector<typename T::Id>  uids;
             uids.reserve(objects.size());
             for (const T &object : objects) {