Fix drop pixels when drag/modifying tag range while transform state is active (fiix #4375)

[Gasparoken]

Before this fix, aseprite displayed an error message instead of dropping pixels.

Issue #4375 was originally due to a crash when dragging a tag while the transformation was active. But it was fixed via https://github.com/aseprite/aseprite/commit/7905acf38a8114c13270bed61305851642454e31 (related to https://github.com/aseprite/aseprite/issues/4367), then the original action resulted in an error message, additionally canceling the dragging of the label range.

fix #4375