Gradients cannot be swapped with other gradients if they do not get their properties by referencing another gradient

Steps to reproduce:

• open Inkscape
• create a shape with any gradient
• create a second shape with a different gradient
• Save as gradient-before.svg
• optimize the SVG with scour --set-precision=8 --enable-viewboxing --enable-comment-stripping --remove-descriptive-elements --create-groups --strip-xml-space --strip-xml-prolog --nindent=4 gradient-before.svg gradient-after.svg
• open gradient-after.svg in Inkscape
• Attempt to swap shape 1's gradient with shape 2's gradient

What happened?

The gradients cannot be swapped

What should have happened?

The gradients should be swapped

Inkscape Version and Operating System:

• Inkscape Versions: 0.92.4 (5da689c313, 2019-01-14) and 1.0beta1 (1a794d5274, 2019-11-01)
• Operating System: openSUSE Tumbleweed
• Operating System version: 20191030

Example files:

gradient-before.svg gradient-after.svg

What the title refers to

gradient-before.svg:

    <defs id="defs6">
        <linearGradient id="linearGradient851" inkscape:collect="always">
            <stop id="stop847" offset="0" style="stop-color:#ff0000;stop-opacity:1;" />
            <stop id="stop849" offset="1" style="stop-color:#ff0000;stop-opacity:0;" />
        </linearGradient>
        <linearGradient id="linearGradient841" inkscape:collect="always">
            <stop id="stop837" offset="0" style="stop-color:#0000ff;stop-opacity:1;" />
            <stop id="stop839" offset="1" style="stop-color:#0000ff;stop-opacity:0;" />
        </linearGradient>
        <linearGradient gradientUnits="userSpaceOnUse" y2="64" x2="64" y1="0" x1="0" id="linearGradient843" xlink:href="#linearGradient841" inkscape:collect="always" />
        <linearGradient gradientUnits="userSpaceOnUse" y2="56" x2="131.5" y1="9" x1="84.5" id="linearGradient853" xlink:href="#linearGradient851" inkscape:collect="always" />
    </defs>
    <rect y="0" x="0" height="64" width="64" id="rect835" style="fill:url(#linearGradient843);fill-rule:evenodd;fill-opacity:1" />
    <rect y="9" x="83" height="47" width="50" id="rect845" style="fill:url(#linearGradient853);fill-rule:evenodd;fill-opacity:1" />

gradient-after.svg:

    <defs id="defs6">
        <linearGradient id="linearGradient843" x2="64" y2="64" gradientUnits="userSpaceOnUse">
            <stop id="stop837" stop-color="#00f" offset="0"/>
            <stop id="stop839" stop-color="#00f" stop-opacity="0" offset="1"/>
        </linearGradient>
        <linearGradient id="linearGradient853" x1="84.5" x2="131.5" y1="9" y2="56" gradientUnits="userSpaceOnUse">
            <stop id="stop847" stop-color="#f00" offset="0"/>
            <stop id="stop849" stop-color="#f00" stop-opacity="0" offset="1"/>
        </linearGradient>
    </defs>
    <rect id="rect835" width="64" height="64" fill="url(#linearGradient843)" fill-rule="evenodd"/>
    <rect id="rect845" x="83" y="9" width="50" height="47" fill="url(#linearGradient853)" fill-rule="evenodd"/>

Workarounds:

• Click the unset paint button (not the no paint button!) and then click the gradient button to get the gradient back. This allows the gradient to be swapped again.