Override beEmpty() to deal with ambiguity.
Override beEmpty() to deal with ambiguity.

Alternatively, we could remove the NMBCollection variant and rely on
countElements/CollectionType.

mishimay/Nimble,github/Nimble,jeffh/Nimble,alvinvarghese/Nimble,msdgwzhy6/Nimble,ashfurrow/Nimble,jeffh/Nimble,phatblat/Nimble,alexbasson/Nimble,phatblat/Nimble,msdgwzhy6/Nimble,feinstruktur/Nimble,rbeeger/Nimble,feinstruktur/Nimble,nikita-leonov/Nimble,gfontenot/Nimble,romankl/Nimble,NatashaTheRobot/Nimble,mrackwitz/Nimble,octo-technology/Nimble,makezwl/zhao,nikita-leonov/Nimble,jrmiddle/Nimble,gfontenot/Nimble,abbeycode/Nimble,mrackwitz/Nimble,NatashaTheRobot/Nimble,AnthonyMDev/Nimble,mishimay/Nimble,jeffh/Nimble,dgdosen/Nimble,jrmiddle/Nimble,nikita-leonov/Nimble,feinstruktur/Nimble,alvinvarghese/Nimble,ScottRobbins/Nimble,romankl/Nimble,dgdosen/Nimble,abbeycode/Nimble,rbeeger/Nimble,joemasilotti/Nimble,AnthonyMDev/Nimble,dgdosen/Nimble,briancroom/Nimble,rbeeger/Nimble,gfontenot/Nimble,dgdosen/Nimble,alexbasson/Nimble,ashfurrow/Nimble,romankl/Nimble,alexbasson/Nimble,briancroom/Nimble,romankl/Nimble,alvinvarghese/Nimble,alexbasson/Nimble,makezwl/zhao,msdgwzhy6/Nimble,jrmiddle/Nimble,briancroom/Nimble,octo-technology/Nimble,vtongcoder/Nimble,twobitlabs/Nimble,phatblat/Nimble,mishimay/Nimble,vtongcoder/Nimble,mrackwitz/Nimble,DanielAsher/Nimble,github/Nimble,AnthonyMDev/Nimble,Quick/Nimble,vtongcoder/Nimble,rbeeger/Nimble,ScottRobbins/Nimble,NatashaTheRobot/Nimble,alvinvarghese/Nimble,abbeycode/Nimble,DanielAsher/Nimble,msdgwzhy6/Nimble,octo-technology/Nimble,ScottRobbins/Nimble,joemasilotti/Nimble,twobitlabs/Nimble,DanielAsher/Nimble,mrackwitz/Nimble,octo-technology/Nimble,gfontenot/Nimble,briancroom/Nimble,jrmiddle/Nimble,jeffh/Nimble,Quick/Nimble,makezwl/zhao,Quick/Nimble,ashfurrow/Nimble,joemasilotti/Nimble,twobitlabs/Nimble,abbeycode/Nimble,NatashaTheRobot/Nimble