[BUG] "Message to client" does not support some special characters

[matKlju]

Bug description:
When using some special characters in "Message to client" and testing in Test Widget, the characters are not diplayed properly or give an error

Expected behavior:
Should be able to handle most special characters

Additional information:

  \t - does not recognize Tab indentation - ignored
  : - ignored, unless preceded by any characrers
  - - Unknown error, unless preceded by any characrers
  _- Unknown error, unless preceded by any characrers
  * - Unknown error
  ~ - Unknown error
  ` - Unknown error
  ' - displays HTML entity (')
  " - displays HTML entity (")
  & - displays HTML entity ("&")
  = - displays HTML entity ("=") or Unknown error if preceded by any characters
  < - displays HTML entity (&lt;)
  >- displays HTML entity (&gt;)