Fix debug logging not to crash when a null block is pushed.
Fix debug logging not to crash when a null block is pushed.

The CompileBlock opcode does a stack.pushNull() when there is no block.

lbdm44/glimmer-vm,tildeio/glimmer,glimmerjs/glimmer-vm,tildeio/glimmer,glimmerjs/glimmer-vm,lbdm44/glimmer-vm,tildeio/glimmer,lbdm44/glimmer-vm,glimmerjs/glimmer-vm