…space.

browsers seem to interpret this differently. Chrome will play animation
twice while Firefox will play animation once.

To work around this strangeness we can remove the loop count completely from
the GIF and this seems to be interpreted as "play once only" by all browsers.

it was not defined

so it REALLY reset frameSources, and doesnt break when you call create() multiple times (as in a loop)

$mode removed

$this->frameSources=[];

Merging test by bosz

# Conflicts:
#	src/GifCreator/GifCreator.php