If vc_error_hdlr is undef we can drop off the end of a func w/o return
If vc_error_hdlr is undef we can drop off the end of a func w/o return

It is always defined as it looks right now, but GCC doesn't know this
and warns that it is possible to exit the function without having set a
return value. Putting an exit(-1) in case vc_error_hdlr is not defined
fixes this warning.

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