You added a couple of BG/VSL BBs from your resource to your composition. Then you hit play …. and oops … a new console message is there, saying something like "input error!".
Ok, maybe you forgot to attach a local parameter to one of the BBs … but where? To make a long story short, always prefix you error message with a context identifier. For example, you write a VSL BB that modifies a texture … it might happen that you, or somebody else using that BB, will forget to attach a parameter to it and dang your code creates an exception if you don't check it.
if( NULL != sourceTexture )
// my code here
bc.OutputToConsole("BB_NameHere: Input error! No source texture available");
If you want to check for availability of objects using the schematic, you can use my VSL BB TestForNull.