Don't crash when trying to export linked parts

Fixes issue #1176

indra/newview/awavefront.cpp

@@ -275,6 +275,13 @@ namespace
 		{
 			if (LLObjectSelectionHandle selection = LLSelectMgr::getInstance()->getSelection())
 			{
+				if (!selection->getFirstRootObject())
+				{
+					if (gSavedSettings.getBOOL("OBJExportNotifyFailed"))
+						LLNotificationsUtil::add("ExportFailed");
+					return true;
+				}
+
 				WavefrontSaver* wfsaver = new WavefrontSaver; // deleted in callback
 				wfsaver->offset = -selection->getFirstRootObject()->getRenderPosition();
 				S32 total = 0;

indra/newview/daeexport.cpp

@@ -272,7 +272,9 @@ public:
 
 	void addSelectedObjects()
 	{
-		if (LLObjectSelectionHandle selection = LLSelectMgr::getInstance()->getSelection())
+		LLObjectSelectionHandle selection = LLSelectMgr::getInstance()->getSelection();
+
+		if (selection && selection->getFirstRootObject())
 		{
 			mSaver.mOffset = -selection->getFirstRootObject()->getRenderPosition();
 			mObjectName = selection->getFirstRootNode()->mName;
@@ -285,14 +287,15 @@ public:
 				if (!node->getObject()->getVolume() || !DAEExportUtil::canExportNode(node)) continue;
 				mSaver.add(node->getObject(), node->mName);
 			}
+		}
 
-			if (mSaver.mObjects.empty())
-			{
-				LLNotificationsUtil::add("ExportFailed");
-				close();
-				return;
-			}
-
+		if (mSaver.mObjects.empty())
+		{
+			LLNotificationsUtil::add("ExportFailed");
+			close();
+		}
+		else
+		{
 			mSaver.updateTextureInfo();
 			mNumTextures = mSaver.mTextures.size();
 			mNumExportableTextures = getNumExportableTextures();

indra/newview/skins/default/xui/en-us/notifications.xml

@@ -5869,7 +5869,7 @@ Builds with extended hollow or extended hole size do not render properly on othe
    icon="alertmodal.tga"
    name="ExportFailed"
    type="alertmodal">
-Bad permissions for the exported object. Export aborted.
+None of the selected objects are exportable. Export aborted.
   </notification>
 
   <notification