fix(emacs/load-lean.el): proceed even if logo image is not created
fix(emacs/load-lean.el): proceed even if logo image is not created

On OSX + emacs-24.5, pgm file is not supported in the terminal.
This patch ignores the error and does not show the Lean logo if it fails to create one.

leanprover/lean,leanprover-community/lean,javra/lean,avigad/lean,leanprover/lean,rlewis1988/lean,dselsam/lean,soonhokong/lean,soonhokong/lean-osx,rlewis1988/lean,soonhokong/lean-osx,leodemoura/lean,soonhokong/lean-windows,soonhokong/lean-windows,leodemoura/lean,fpvandoorn/lean,fgdorais/lean,johoelzl/lean,fpvandoorn/lean2,fpvandoorn/lean2,leanprover/lean,digama0/lean,fgdorais/lean,soonhokong/lean-osx,leanprover-community/lean,dselsam/lean,johoelzl/lean,avigad/lean,dselsam/lean,digama0/lean,Kha/lean,rlewis1988/lean,leanprover/lean,digama0/lean,digama0/lean,leanprover-community/lean,leanprover-community/lean,UlrikBuchholtz/lean,soonhokong/lean,soonhokong/lean,javra/lean,Kha/lean,rlewis1988/lean,soonhokong/lean-osx,dselsam/lean,fgdorais/lean,fpvandoorn/lean,fgdorais/lean,dselsam/lean,avigad/lean,levnach/lean,fgdorais/lean,soonhokong/lean-windows,UlrikBuchholtz/lean,digama0/lean,javra/lean,avigad/lean,javra/lean,soonhokong/lean,javra/lean,soonhokong/lean-osx,rlewis1988/lean,fpvandoorn/lean2,johoelzl/lean,johoelzl/lean,soonhokong/lean,johoelzl/lean,leanprover/lean,fpvandoorn/lean,avigad/lean,johoelzl/lean,avigad/lean,leodemoura/lean,fpvandoorn/lean2,fpvandoorn/lean2,Kha/lean,rlewis1988/lean,soonhokong/lean-windows,dselsam/lean,fgdorais/lean,leodemoura/lean,Kha/lean,digama0/lean,leanprover/lean,levnach/lean,leanprover-community/lean,levnach/lean,leanprover-community/lean,fpvandoorn/lean,fpvandoorn/lean,soonhokong/lean-windows,fpvandoorn/lean,UlrikBuchholtz/lean,UlrikBuchholtz/lean,Kha/lean,levnach/lean,leodemoura/lean,UlrikBuchholtz/lean,levnach/lean,leodemoura/lean,Kha/lean