Wrong charset used in creating search terms when server supports UTF8

[axandar]

Describe the bug
Function int[] search(String msgSequence, SearchTerm term) throws ProtocolException, SearchException on line 2479 in IMAPProtocol class checks if server support UTF8.
In function private int[] issueSearch(String msgSequence, SearchTerm term, String charset) throws ProtocolException, SearchException, IOException on line 2532 Argument object is created with charset as null.

When null is passed to SearchSequence#generateSequence() it defaults to all ASCII text while parsing strings in seach terms.

I don't know if reproduction is needed here.

[lukasj]

simple reproducer and/or test for this would be appreciated as the code path itself may not be clear and straightforward to newcomers to this project...

[jmehrens]

Looks like PR #607 is was created by another user for this issue. From what I can tell the PR looks correct but need to review it properly.