Hi,

in [1], Ihor fixed a bug I reported in ox-odt. Unfortunately, this fix
broke figures with several lines of captions such as:

    #+CAPTION: first line,
    #+CAPTION: second line
    [[file:media/myPicture.png]]

This is because, in this case, org-odt-plain-text is called at some
point with " " as value for `text`. In this context, both `leading` and
`trailing` temporary variables contain the same value as `text`, making
the `substring` call crash.

The attached patch fixes the issue by considering that there is no
leading/trailing content when the input only contains spaces.

Best

[1] https://list.orgmode.org/orgmode/87v8i3y135.fsf@cassou.me/

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-- 
Damien Cassou

"Success is the ability to go from one failure to another without
losing enthusiasm." --Winston Churchill