fireSearchEvent only if it's not an empty string

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@27812 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
GeoGebraCASIntegrationTest:

Added test cases for ticket #3385,
maintained some test cases.

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@27813 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
minor fixes

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@27814 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e