In Inkscape 1.0alpha (1:0.92.0+devel+201904112206+331007d) I can't reproduce this error anymore.
It seems like the resolution now is that an "unfinished" fill will just refuse to be created.
So you have to zoom in completely (or at least close enough) to properly fill – or nothing happens when clicking that fill tool.
In Inkscape 1.0alpha (1:0.92. 0+devel+ 201904112206+ 331007d) I can't reproduce this error anymore.
It seems like the resolution now is that an "unfinished" fill will just refuse to be created.
So you have to zoom in completely (or at least close enough) to properly fill – or nothing happens when clicking that fill tool.
Closing because cannot reproduce.
Closed by: https:/ /gitlab. com/mray