Changing formatting of superscript text causes baseline errors

[Martin Smith]

Inkscape 0.92.1 r15371, Windows 10

Changing formatting of superscript text causes misalignment

To reproduce:

Create a new text object and type "10x"
Highlight the "x" and click the "Toggle superscript" button, then Ctrl-I for italic type
Type "+1" after the "x" - this will appear in superscript as expected
Highlight the "+1" and key Ctrl-I to de-italicize

The "+1" now jumps up to a higher baseline. Clicking "Toggle superscript" returns it to its correct position, in line with the "x". Clicking "Toggle superscript" again places the "+1" on the text baseline (non-superscript).