cli: sprite selection only works when specifying output directory

[bunder2015]

noticed this while testing sprite fixes...

$ ./dwrandomizer dw.nes IVIAAVCEKACBAAAAKAAAAYAU 8495643497209177 "DW3 Ghost"
DWRandomizer version 3.0.3 beta 672
Randomizing using seed: 8495643497209177 with flags IVIAAVCEKACBAAAAKAAAAYAU
Using seed# 8495643497209177
Using flags IVIAAVCEKACBAAAAKAAAAYAU
Applying various patches...
Shuffling chest contents...
Mapping Dungeons...
Checking quest item placement...
Disallowing Armor in Charlock...
Checking for key availability...
Generating a small map
Compressed map size: 1720
Randomizing enemy attack patterns...
Randomizing enemy zone layout...
Randomizing monsters in enemy zones...
Randomizing weapon shop inventory...
Randomizing stat growth...
Randomizing spell learning...
Modifying enemy drops...
Changing MP requirements for spells...
Changing required experience to 50% of normal...
Fixing the fighter's ring...
Adding functionality to the death necklace...
Enabling menu cursor wrap-around...
Enabling speed hacks...
Reducing early metal rewards...
Making torches and fairy water more deadly...
Making repel work in dungeons...
Illuminating all the caves...
Modifying run rate for high level monsters...
Updating title screen...
Skipping original credits...
Setting player sprite to DW3 Female Goof-off...
Checksum: b5f1caeb79d51a15
Unable to open file 'DW3 Ghost/DWRando.8495643497209177.IVIAAVCEKACBAAAAKAAAAYAU.nes' for writing

$ ./dwrandomizer dw.nes IVIAAVCEKACBAAAAKAAAAYAU 8495643497209177 "DW3 Ghost" .
DWRandomizer version 3.0.3 beta 672
Randomizing using seed: 8495643497209177 with flags IVIAAVCEKACBAAAAKAAAAYAU
Using seed# 8495643497209177
Using flags IVIAAVCEKACBAAAAKAAAAYAU
Applying various patches...
Shuffling chest contents...
Mapping Dungeons...
Checking quest item placement...
Disallowing Armor in Charlock...
Checking for key availability...
Generating a small map
Compressed map size: 1720
Randomizing enemy attack patterns...
Randomizing enemy zone layout...
Randomizing monsters in enemy zones...
Randomizing weapon shop inventory...
Randomizing stat growth...
Randomizing spell learning...
Modifying enemy drops...
Changing MP requirements for spells...
Changing required experience to 50% of normal...
Fixing the fighter's ring...
Adding functionality to the death necklace...
Enabling menu cursor wrap-around...
Enabling speed hacks...
Reducing early metal rewards...
Making torches and fairy water more deadly...
Making repel work in dungeons...
Illuminating all the caves...
Modifying run rate for high level monsters...
Updating title screen...
Skipping original credits...
Setting player sprite to DW3 Ghost...
Checksum: b5f1caeb79d51a15