Import: Use default values for the session settings if they are not set

Exporting messed up sessions is not working. Somehow for one session the sound config wasn't exported and for another one the theme. Both sessions are rejected when I try to import them. Can't we use default values here if the appropriate values are not set?

runde2-3_6_2016.json runde3-3_6_2016.json

Server error:

I20160603-20:42:58.104(2)? Exception while invoking method 'HashtagsCollection.import' Error: Music volume is required
I20160603-20:42:58.105(2)?     at getErrorObject (packages/aldeed_collection2-core/lib/collection2.js:437:1)
I20160603-20:42:58.105(2)?     at [object Object].doValidate (packages/aldeed_collection2-core/lib/collection2.js:420:1)
I20160603-20:42:58.105(2)?     at [object Object].Mongo.Collection.(anonymous function) [as insert] (packages/aldeed_collection2-core/lib/collection2.js:173:1)
I20160603-20:42:58.105(2)?     at [object Object].HashtagsCollectionImport (shared/hashtags.js:158:23)
I20160603-20:42:58.105(2)?     at maybeAuditArgumentChecks (packages/ddp-server/livedata_server.js:1704:12)
I20160603-20:42:58.105(2)?     at packages/ddp-server/livedata_server.js:711:19
I20160603-20:42:58.105(2)?     at [object Object]._.extend.withValue (packages/meteor/dynamics_nodejs.js:56:1)
I20160603-20:42:58.106(2)?     at packages/ddp-server/livedata_server.js:709:40
I20160603-20:42:58.106(2)?     at [object Object]._.extend.withValue (packages/meteor/dynamics_nodejs.js:56:1)
I20160603-20:42:58.106(2)?     at packages/ddp-server/livedata_server.js:707:46
I20160603-20:42:58.106(2)? Sanitized and reported to the client as: Music volume is required [400]
I20160603-20:42:58.106(2)? 
I20160603-20:43:25.942(2)? Exception while invoking method 'HashtagsCollection.import' Error: Theme is required
I20160603-20:43:25.943(2)?     at getErrorObject (packages/aldeed_collection2-core/lib/collection2.js:437:1)
I20160603-20:43:25.943(2)?     at [object Object].doValidate (packages/aldeed_collection2-core/lib/collection2.js:420:1)
I20160603-20:43:25.943(2)?     at [object Object].Mongo.Collection.(anonymous function) [as insert] (packages/aldeed_collection2-core/lib/collection2.js:173:1)
I20160603-20:43:25.943(2)?     at [object Object].HashtagsCollectionImport (shared/hashtags.js:158:23)
I20160603-20:43:25.943(2)?     at maybeAuditArgumentChecks (packages/ddp-server/livedata_server.js:1704:12)
I20160603-20:43:25.943(2)?     at packages/ddp-server/livedata_server.js:711:19
I20160603-20:43:25.944(2)?     at [object Object]._.extend.withValue (packages/meteor/dynamics_nodejs.js:56:1)
I20160603-20:43:25.944(2)?     at packages/ddp-server/livedata_server.js:709:40
I20160603-20:43:25.944(2)?     at [object Object]._.extend.withValue (packages/meteor/dynamics_nodejs.js:56:1)
I20160603-20:43:25.944(2)?     at packages/ddp-server/livedata_server.js:707:46
I20160603-20:43:25.944(2)? Sanitized and reported to the client as: Theme is required [400]