Fix a writing mistake
Fix a writing mistake

A small mistake found in the line of ```The default error is "can't be empty"``` for ```:presence``` helper. ```empty``` word changed to ```blank```.
arjes/rails,ttanimichi/rails,samphilipd/rails,tgxworld/rails,88rabbit/newRails,MichaelSp/rails,sealocal/rails,georgeclaghorn/rails,baerjam/rails,amoody2108/TechForJustice,EmmaB/rails-1,yasslab/railsguides.jp,vipulnsward/rails,illacceptanything/illacceptanything,Sen-Zhang/rails,maicher/rails,shioyama/rails,marklocklear/rails,amoody2108/TechForJustice,printercu/rails,elfassy/rails,esparta/rails,palkan/rails,alecspopa/rails,esparta/rails,mohitnatoo/rails,kmcphillips/rails,hanystudy/rails,EmmaB/rails-1,lcreid/rails,deraru/rails,rafaelfranca/omg-rails,odedniv/rails,illacceptanything/illacceptanything,kmcphillips/rails,prathamesh-sonpatki/rails,illacceptanything/illacceptanything,bolek/rails,mohitnatoo/rails,deraru/rails,tjschuck/rails,gcourtemanche/rails,gavingmiller/rails,gavingmiller/rails,notapatch/rails,deraru/rails,felipecvo/rails,mijoharas/rails,kmcphillips/rails,schuetzm/rails,jeremy/rails,brchristian/rails,gauravtiwari/rails,mtsmfm/railstest,bogdanvlviv/rails,rossta/rails,deraru/rails,rafaelfranca/omg-rails,riseshia/railsguides.kr,notapatch/rails,MSP-Greg/rails,Envek/rails,arunagw/rails,georgeclaghorn/rails,tjschuck/rails,gauravtiwari/rails,flanger001/rails,esparta/rails,kddeisz/rails,pvalena/rails,mechanicles/rails,Sen-Zhang/rails,sergey-alekseev/rails,coreyward/rails,yalab/rails,felipecvo/rails,assain/rails,mechanicles/rails,Edouard-chin/rails,xlymian/rails,riseshia/railsguides.kr,kenta-s/rails,notapatch/rails,tijwelch/rails,prathamesh-sonpatki/rails,flanger001/rails,Edouard-chin/rails,vassilevsky/rails,EmmaB/rails-1,mechanicles/rails,mathieujobin/reduced-rails-for-travis,rossta/rails,richseviora/rails,yalab/rails,lcreid/rails,jeremy/rails,iainbeeston/rails,Spin42/rails,Erol/rails,Vasfed/rails,illacceptanything/illacceptanything,untidy-hair/rails,yasslab/railsguides.jp,gfvcastro/rails,illacceptanything/illacceptanything,esparta/rails,voray/rails,palkan/rails,Vasfed/rails,joonyou/rails,yhirano55/rails,travisofthenorth/rails,rbhitchcock/rails,rails/rails,brchristian/rails,mtsmfm/rails,kamipo/rails,voray/rails,bogdanvlviv/rails,starknx/rails,mohitnatoo/rails,starknx/rails,marklocklear/rails,lcreid/rails,baerjam/rails,vipulnsward/rails,schuetzm/rails,illacceptanything/illacceptanything,BlakeWilliams/rails,gavingmiller/rails,joonyou/rails,repinel/rails,xlymian/rails,yasslab/railsguides.jp,tijwelch/rails,yawboakye/rails,flanger001/rails,assain/rails,betesh/rails,travisofthenorth/rails,kmayer/rails,mathieujobin/reduced-rails-for-travis,pschambacher/rails,sergey-alekseev/rails,yahonda/rails,travisofthenorth/rails,starknx/rails,aditya-kapoor/rails,gfvcastro/rails,marklocklear/rails,bolek/rails,yhirano55/rails,betesh/rails,gcourtemanche/rails,kirs/rails-1,MichaelSp/rails,alecspopa/rails,arjes/rails,kddeisz/rails,maicher/rails,eileencodes/rails,amoody2108/TechForJustice,printercu/rails,coreyward/rails,illacceptanything/illacceptanything,fabianoleittes/rails,pschambacher/rails,MSP-Greg/rails,Envek/rails,arunagw/rails,samphilipd/rails,illacceptanything/illacceptanything,gfvcastro/rails,Erol/rails,Envek/rails,tijwelch/rails,eileencodes/rails,ledestin/rails,bradleypriest/rails,baerjam/rails,stefanmb/rails,ngpestelos/rails,alecspopa/rails,shioyama/rails,elfassy/rails,vassilevsky/rails,pvalena/rails,joonyou/rails,bradleypriest/rails,prathamesh-sonpatki/rails,baerjam/rails,ledestin/rails,mathieujobin/reduced-rails-for-travis,kenta-s/rails,eileencodes/rails,Erol/rails,yasslab/railsguides.jp,lucasmazza/rails,hanystudy/rails,bogdanvlviv/rails,yhirano55/rails,schuetzm/rails,untidy-hair/rails,Stellenticket/rails,illacceptanything/illacceptanything,koic/rails,fabianoleittes/rails,richseviora/rails,rbhitchcock/rails,riseshia/railsguides.kr,maicher/rails,brchristian/rails,Edouard-chin/rails,bogdanvlviv/rails,koic/rails,eileencodes/rails,ttanimichi/rails,matrinox/rails,printercu/rails,yalab/rails,Envek/rails,tjschuck/rails,fabianoleittes/rails,kachick/rails,palkan/rails,illacceptanything/illacceptanything,kamipo/rails,palkan/rails,yahonda/rails,tgxworld/rails,richseviora/rails,Stellenticket/rails,kmcphillips/rails,samphilipd/rails,kmayer/rails,bradleypriest/rails,rbhitchcock/rails,assain/rails,88rabbit/newRails,rails/rails,pvalena/rails,printercu/rails,MichaelSp/rails,kamipo/rails,rails/rails,koic/rails,ledestin/rails,illacceptanything/illacceptanything,matrinox/rails,Edouard-chin/rails,illacceptanything/illacceptanything,hanystudy/rails,Vasfed/rails,mtsmfm/railstest,shioyama/rails,BlakeWilliams/rails,BlakeWilliams/rails,untidy-hair/rails,yalab/rails,flanger001/rails,Stellenticket/rails,BlakeWilliams/rails,sergey-alekseev/rails,lucasmazza/rails,vassilevsky/rails,pschambacher/rails,iainbeeston/rails,bolek/rails,gauravtiwari/rails,illacceptanything/illacceptanything,aditya-kapoor/rails,assain/rails,vipulnsward/rails,jeremy/rails,gcourtemanche/rails,repinel/rails,sealocal/rails,kirs/rails-1,arunagw/rails,yawboakye/rails,elfassy/rails,utilum/rails,illacceptanything/illacceptanything,aditya-kapoor/rails,tjschuck/rails,voray/rails,joo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