DVB: The content of the "Information" panel was lost when changing the UI language.

Fixes 4993.
DVB: Correctly enable the "Information" panel when clicking the "Info" button.

Previously, enabling the "Information" panel using the "Info" button on the "Navigation" dialog would reduce the size of the main window when hiding the panel from the "View" menu.

Fixes #4992
Don't force any background color for the Shockwave graph.

This commit fixes #1747.
WebUI: Inform the web interface that no audio stream is available.