Incorrect result numbers for partial updates if there is an error

When a multi update is applied to a collection where the operation is unable to be applied to all documents (e.g. a $inc on an array field), getLastError() returns "n" : 0 with the error but the operation still updates documents that it is able to update. The multi-update returns as soon as it fails to apply an operation.

Expected behavior: It should report "n" : `count of the number of documents it was able to update` as well as the error.

Actual behavior: Reports error and "n" : 0.

The example below updates 1/2 documents, but returns "n" : 0

>use test

>db.c.insert({a:3,b:4})

>db.c.insert({a:[3,5],b:3})

>db.c.find()

{ "_id" : ObjectId("511d4e76242fb0dfc20856cc"), "a" : [ 3, 5 ], "b" : 3 }

{ "_id" : ObjectId("511d4e9f242fb0dfc20856cd"), "a" : 3, "b" : 4 }

>db.c.update({}, {$inc:{a:1,b:6}}, {multi:true});db.getLastErrorObj();

{

	"err" : "Cannot apply $inc modifier to non-number",

	"code" : 10140,

	"n" : 0,

	"connectionId" : 1,

	"ok" : 1

}

> db.c.find()

{ "_id" : ObjectId("511d4ed0242fb0dfc20856ce"), "a" : 4, "b" : 10 }

{ "_id" : ObjectId("511d4edd242fb0dfc20856cf"), "a" : [ 3, 5 ], "b" : 3 }