Fix #5065: Anomaly: Not a proof by induction
Fix #5065: Anomaly: Not a proof by induction

Using abstract can create beta-redexes or let-ins in the head of the
proof terms. The code projecting out mutual lemmas was not robust
enough.

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