Bug in contourf 3.0.4-RC3

[Marco Caliari]

Dear maintainers,

contourf(peaks)

in 3.0.4-RC3 produces a nice cyan rectangle. The problem appears to be 
related with line 171 in contourf.m

for n = 1:len

which was in 3.0.3 e.g.,

for n = len:-1:1

Best regards,

Marco