Lucid Sunlight authored Nov 17, 2020 and Dmitry Kazakov committed Nov 17, 2020

Previously, we would only check the index of the tab we're on,
which would work as expected in `Rich Text Only` and `Both` editor modes.
But in `SVG Source Only` mode, it would mistakenly think we're on
rich text editor, instead of SVG editor.

That breaks saving, as we were trying to save text document instead of SVG.
Would crash in `KoSvgTextShapeMarkupConverter::convertDocumentToSvg`
as the text document would have no text.
Or empty the text object if we try to avoid the crash.