1) is sounds like the variable "%blockno " does not have a value. there is no value to use.
2) no line number in the program.
3) each line in the controler usually has a line number.
a) blockno is another name for line number.
4) did you change anything in the post itself?
a) leaving out perhaps a ";" or something else.
5) my last thought
something about an improper "size" sticks in my mind.