[R] Strange error returned or bug in gam in mgcv????

[Corrado]

Dear friends,

what is this error message in gam???? I cannot understand what it means .... 
is it a bug?

gam_bray_scot24_pc_0505<gam(bray~s(PC1,PC2,PC3,PC4,PC5,
PC1.1,PC2.1,PC3.1,PC4.1,PC5.1),data=dist_scot24_vector_with_climate)

Error in if (length(data) != vl) { :
  missing value where TRUE/FALSE needed
Calls: gam ... smooth.construct -> smooth.construct.tp.smooth.spec -> array
In addition: Warning message:
In array(0, n * k) : NAs introduced by coercion
Execution halted

Thanks in advance,

Best regards
-- 
Corrado Topi

Global Climate Change & Biodiversity Indicators
Area 18,Department of Biology
University of York, York, YO10 5YW, UK
Phone: + 44 (0) 1904 328645, E-mail: ct529 at york.ac.uk