Cvs log -S crashes when tag doesn't exist.

[Clinton Pierce]

Using the command:

        cvs log -S -rmigration1:: foo.c

Causes a memory error if the file foo.c doesn't contain the tag migration1.
This crops up when I'm trying to see all of the changes for a component like
this:

        cvs log -S -rmigration1:: mycomponent\*.c

And the new file happens to get swept up in the glob.

I'm using the Windows Binary, version 1.11.4.