thin_metadata_size: check for block size > 0

thin-provisioning/thin_metadata_size

@@ -37,6 +37,7 @@ end
 
 def check_opts(opts)
   abort "#{$prg} - 3 arguments required!" if opts.length < 3
+  abort "#{$prg} - block size must be > 0" if opts[:blocksize] <= 0
   abort "#{$prg} - poolsize must be much larger than blocksize" if opts[:poolsize] < opts[:blocksize]
   abort "#{$prg} - maximum number of thin provisioned devices must be > 0" if opts[:maxthins].nil? || opts[:maxthins] == 0
 end