[LyX/master] Fix make check after parfill(skip) bump.

[Pavel Sanda]

commit 5ef5f9e919fbe0ded7cdccbd8ea675ec56c19e28
Author: Pavel Sanda <sanda at lyx.org>
Date:   Tue Aug 4 00:23:48 2026 +0200

    Fix make check after parfill(skip) bump.
    
    https://mail-archive.com/lyx-devel@lists.lyx.org/msg226635.html
---
 src/support/Length.cpp    | 4 +++-
 src/tests/regfiles/Length | 2 ++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/support/Length.cpp b/src/support/Length.cpp
index cdc0049e36..4305b2802a 100644
--- a/src/support/Length.cpp
+++ b/src/support/Length.cpp
@@ -254,7 +254,9 @@ double Length::inInch(double text_width, double em_width, double margin) const
 		break;
 	case FIL:
 	case Length::UNIT_NONE:
-		result = 0;  // this cannot happen
+		// FIL is stretchable glue and UNIT_NONE has no unit;
+		// neither has a fixed length, so treat as 0.
+		result = 0;
 		break;
 	}
 	return result;
diff --git a/src/tests/regfiles/Length b/src/tests/regfiles/Length
index 1922641b5f..4a644b177c 100644
--- a/src/tests/regfiles/Length
+++ b/src/tests/regfiles/Length
@@ -4,6 +4,7 @@
 2495925 pix(250) = 2342dd
 23332503 pix(250) = 2342em
 10044643 pix(250) = 2342ex
+0 pix(250) = 2342fil
 168624000 pix(250) = 2342in
 6638740 pix(250) = 2342mm
 1296250 pix(250) = 2342mu
@@ -24,6 +25,7 @@
 2496 BP = 2342dd
 23333 BP = 2342em
 10045 BP = 2342ex
+0 BP = 2342fil
 168624 BP = 2342in
 6639 BP = 2342mm
 1296 BP = 2342mu