[toplevel] Don't check proofs in -quick mode.
[toplevel] Don't check proofs in -quick mode.

This fixes a logical error introduced in
ce2b2058587224ade9261cd4127ef4f6e94d356b

Patch by @gares, closes https://coq.inria.fr/bugs/show_bug.cgi?id=5484

coq/coq,amintimany/coq,Zimmi48/coq,Zimmi48/coq,coq/coq,ejgallego/coq,Zimmi48/coq,Lionel-Rieg/coq,coq/coq,maximedenes/coq,letouzey/coq-wip,Matafou/coq,silene/coq,ppedrot/coq,ejgallego/coq,gares/coq,JasonGross/coq,ppedrot/coq,maximedenes/coq,amintimany/coq,letouzey/coq-wip,ppedrot/coq,JasonGross/coq,maximedenes/coq,Matafou/coq,Matafou/coq,silene/coq,Lionel-Rieg/coq,Zimmi48/coq,SkySkimmer/coq,william-lawvere/coq,william-lawvere/coq,SkySkimmer/coq,gares/coq,JasonGross/coq,letouzey/coq-wip,letouzey/coq-wip,maximedenes/coq,Lionel-Rieg/coq,ppedrot/coq,silene/coq,SkySkimmer/coq,coq/coq,gares/coq,letouzey/coq-wip,amintimany/coq,ejgallego/coq,JasonGross/coq,ejgallego/coq,SkySkimmer/coq,ppedrot/coq,gares/coq,maximedenes/coq,gares/coq,william-lawvere/coq