fix file input: handle undefined value
fix file input: handle undefined value

This update permit user to reset the value of the file input. It is useful for modal edition for example.

bijeeshtk/lumx,clementprevot/lumX,b-cuts/lumX,bright-sparks/lumX,ezzye/write-to-be-heard,bijeeshtk/lumx,terradatum/lumX,jayaguilar/lumX,bright-sparks/lumX,jayaguilar/lumX,jason588/lumX,jefvel/lumX,hinablue/lumX,terradatum/lumX,ezzye/write-to-be-heard,b-cuts/lumX,jefvel/lumX,cupceavictor/lumX,cupceavictor/lumX,clementprevot/lumX,ezzye/write-to-be-heard,lumapps/lumX,noikiy/lumX,cupceavictor/lumX,jason588/lumX,daniel-oliveiravas/lumX,terradatum/lumX,daniel-oliveiravas/lumX,Ener-Getick/lumX,b-cuts/lumX,lumapps/lumX,cupceavictor/lumX,itxd/lumX,daniel-oliveiravas/lumX,clementprevot/lumX,itxd/lumX,itxd/lumX,lumapps/lumX,jason588/lumX,jefvel/lumX,b-cuts/lumX,bright-sparks/lumX,hinablue/lumX,bijeeshtk/lumx,noikiy/lumX,jayaguilar/lumX,bijeeshtk/lumx,ezzye/write-to-be-heard,clementprevot/lumX,jason588/lumX,Ener-Getick/lumX,Ener-Getick/lumX,terradatum/lumX,noikiy/lumX,jayaguilar/lumX,hinablue/lumX,noikiy/lumX,lumapps/lumX,itxd/lumX,bright-sparks/lumX,daniel-oliveiravas/lumX,hinablue/lumX,Ener-Getick/lumX,jefvel/lumX