Crash dragging selected text from warning box

Edit a cpp code file containing code that produces a warning (yellow triangle and text on right margin of edit window). Mouse over the warning and a yellow text box with more info appears. Mouse over text box then click and drag and release, to select some of the text. Click the selected text and drag out of the text box as if to drop it in the file. The program crashes with a segmentation fault.

QtCreator is running on RHEL 7.5 with graphics going via ssh -X (PuTTY) connection to a Windows machine running the VcXsrv X11 server, which may or may not be contributing to the problem.

When QtCreator starts it prints two warnings to the terminal: "No matching fbConfigs or visuals found," and, "failed to load driver: swrast." Those also may or may not be related.