[LyX/master] Correctly show merged paragraphs with ct in plain text output

[Juergen Spitzmueller]

commit 117e63b01b9642b2bbb6ae421bb57f12a23579f1
Author: Juergen Spitzmueller <spitz at lyx.org>
Date:   Fri Dec 27 09:01:06 2019 +0100

    Correctly show merged paragraphs with ct in plain text output
    
    Fixes #3137
---
 src/output_plaintext.cpp |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/output_plaintext.cpp b/src/output_plaintext.cpp
index 8c5655d..9dae951 100644
--- a/src/output_plaintext.cpp
+++ b/src/output_plaintext.cpp
@@ -56,9 +56,11 @@ void writePlaintextFile(Buffer const & buf, odocstream & os,
 	ParagraphList::const_iterator end = par.end();
 	ParagraphList::const_iterator it = beg;
 	for (; it != end; ++it) {
+		bool const merged_par = (*it).parEndChange().deleted();
 		writePlaintextParagraph(buf, *it, os, runparams, ref_printed);
-		os << "\n";
-		if (runparams.linelen > 0)
+		if (!merged_par)
+			os << "\n";
+		if (runparams.linelen > 0 && !merged_par)
 			os << "\n";
 	}
 }