feat(indicator): fix error message popup

The error message popup was showing empty with the following error message showing in the stderr:

</i>' from markup due to error parsing markup: Error on line 2 char 45: “ ” is not a valid character following a “<” character; it may not begin an element name

It is happening because the error message sometimes contain either < or > characters, the XML markup was trying to interpret that as a tag and failing instead.

This commit fixes it by escaping the text to be XML safe.

Before:

After: