Prevent exception when filename is given.

[obiwankennedy]

just a short fix, I have issue about textclip, so I fixed it for me, and make the fix available here. Perhaps, it is a logic error. I did not check that. but at least you know that there is something strange around this code when passing a filename argument.

My textCilp construction is:
txtclip = TextClip(filename="/home/user/path/to/where/i/want/{}".format(text),font="Inria-Sans",fontsize=150, color="white")

[coveralls]

Coverage remained the same at 67.448% when pulling 12dbeaa on obiwankennedy:owk_filename_for_text into e8ce135 on Zulko:master.

[tburrows13]

Thanks for the fix. I'll get round to checking this properly soon.

[tburrows13]

Agreed, this is a logic error: If txt == None and temptxt is not provided, then it will crash (as you found). I can't work out why tempfilename would end up being None, but I think that it is a good idea to clean up regardless of logic earlier in the function.

It was introduced here: https://github.com/Zulko/moviepy/pull/1077/files?file-filters%5B%5D=.md#diff-d6e691a0e95fa49e49448058435572cbL147 without taking into consideration that vector can be a numpy array.