Evolution 3.48.3 is not showing HTML mail contents correctly when plain text is set as the default display mode. This bug is not present in version 3.48.0.
Precisely, the problem arises when you set the preferences to show html parts as attachments and to always show plain text. When you pick an email containing html parts, scroll all the way down and finally click the html content button to enlarge the html preview area: such area will be so small that it won't let you see anything. The width looks correct but the height doesn't, until you resize the Evolution window and force it the redraw the contents.

I guess ResizeObserver not working as expected, as this issue can be worked around by commenting out line 1358 in /usr/share/evolution/webkit/e-web-view.js (Evo.mailDisplayResizeObserver.observe(doc.body);)


Reproducible: Always

Steps to Reproduce:
1. enable "Show suppressed HTML parts as attachments" and set the "HTML Mode" to "Only ever show plain text" in the preferences (Preferences -> Mail Preferences -> HTML Messages).
2. pick any email with html contents and scroll all the way down, till you reach the "HTML document attachment" button, then click it to enlarge the HTML content preview.
3. the HTML area has such a very short height that won't let you see anything, until you resize Evolution's window.

Actual Results:  
The html preview area is too small to show anything

Expected Results:  
The html preview area should show the correct height.