Fix InsetBox::contentAlignment()

Some cases where alignment is possible were missing.

Candidate for 2.3.x.

(cherry picked from commit de67b68b1d)

src/insets/InsetBox.cpp

@@ -227,7 +227,9 @@ ColorCode InsetBox::backgroundColor(PainterInfo const &) const
 
 LyXAlignment InsetBox::contentAlignment() const
 {
-	if (!params_.use_makebox)
+	// Custom horizontal alignment is only allowed with a fixed width
+	// and if either makebox or no inner box are used
+	if (params_.width.empty() || !(params_.use_makebox || !params_.inner_box))
 		return LYX_ALIGN_NONE;
 
 	// The default value below is actually irrelevant

status.23x

@@ -248,6 +248,8 @@ What's new
 
 - Fix duplicate, disabled "Separated <Environment> Below" menu item.
 
+- Fix horizontal alignment of some Box types on screen.
+
 
 * INTERNALS