Error in use polar

[kruvalig]

I use octave under windows. On command:

octave.exe:1> t=0:0.1:2*pi; polar(t, sqrt(2+(cos(t)).^2));

i get output:

error: [java] org.octave.graphics.PropertyException: invalid property  
value - zero
error: evaluating for command near line 32, column 11
error: evaluating if command near line 31, column 9
error: evaluating for command near line 29, column 7
error: evaluating if command near line 24, column 5
error: called from `__jhandles_set' in file `D:\Program  
Files\Octave\share\octave\packages\jhandles-0.3.1\__jhandles_set.m'
error: called from `polar' in file `D:\Program  
Files\Octave\share\octave\3.0.0\m\plot\polar.m'

but all work fine, and i see the picture. Why this error appear?