Fixing #4177 (find_projectable was liable to ask to instantiate an evar twice).
Fixing #4177 (find_projectable was liable to ask to instantiate an evar twice).

This is a bug in a pretty old code, showing also in 8.3 and 8.4.

Ptival/coq,gares/coq,mattam82/coq,gares/coq,letouzey/coq-wip,barras/coq,Ptival/coq,coq/coq,JasonGross/coq,ppedrot/coq,TheTypoMaster/coq,ppedrot/coq,barras/coq,mlasson/coq,Matafou/coq,TOSPIO/coq,TheTypoMaster/coq,maximedenes/coq,william-lawvere/coq,letouzey/coq-wip,ppedrot/coq,coq/coq,Zimmi48/coq,mlasson/coq,letouzey/coq-wip,letouzey/coq-wip,SkySkimmer/coq,ejgallego/coq,JasonGross/coq,gares/coq,herbelin/github-coq,8l/coq,william-lawvere/coq,maximedenes/coq,JasonGross/coq,jpdeplaix/coq,gares/coq,silene/coq,silene/coq,coq/coq,ejgallego/coq,letouzey/coq-wip,JasonGross/coq,mlasson/coq,TOSPIO/coq,ppedrot/coq,ejgallego/coq,Matafou/coq,SkySkimmer/coq,silene/coq,jpdeplaix/coq,8l/coq,ppedrot/coq,amintimany/coq,mattam82/coq,TOSPIO/coq,gares/coq,maximedenes/coq,SkySkimmer/coq,jpdeplaix/coq,TheTypoMaster/coq,amintimany/coq,maximedenes/coq,Lionel-Rieg/coq,Ptival/coq,Lionel-Rieg/coq,william-lawvere/coq,Zimmi48/coq,Matafou/coq,amintimany/coq,herbelin/github-coq,ejgallego/coq,herbelin/github-coq,mattam82/coq,coq/coq,Zimmi48/coq,SkySkimmer/coq,barras/coq,maximedenes/coq,Zimmi48/coq,8l/coq,Lionel-Rieg/coq