Save as optimized svg generates invalid svg output

Steps to reproduce bug:

1. Create new document in inkscape
2. Click the text tool
3. Write something, press return, write something, press return, write something
4. Select the three lines of text and set a new font and font-size
5. Save as optimized svg, and make sure the "group collapsing" option is unchecked, and the "create groups for similar attributes" is checked

The generated output svg has a structure like this:

<svg>
  <text>
    <g>
      <tspan>...</tspan>
      <tspan>...</tspan>
      <tspan>...</tspan>
    </g>
  </text>
</svg>

The g tag in this case makes browsers not render the tspans. It's also invalid svg markup, since <g> isn't allowed as a child of <text>.