no need for if(tree)
display the opcode first, followed by the file name

Change-Id: Ic5dd7409414d2f748c326c59a4b850dc2244da1f
Reviewed-on: https://code.wireshark.org/review/3446
Reviewed-by: Martin Kaiser <wireshark@kaiser.cx>
Tested-by: Martin Kaiser <wireshark@kaiser.cx>