Initialize recently added forceownlines_ bool

This adds on to the fix for #8875 (a25569eb).

lib/doc/Customization.lyx

@@ -151,6 +151,7 @@ End
 \html_css_as_file 0
 \html_be_strict true
 \author -712698321 "Jürgen Spitzmüller" 
+\author 274215730 "scott" 
 \end_header
 
 \begin_body
@@ -17070,6 +17071,9 @@ status collapsed
 ] Force a a line break in the LaTeX output before the inset starts and after
  the inset ends.
  This assures the inset itself is output on its own lines, for parsing purposes.
+
+\change_inserted 274215730 1419105878
+ Default is false.
 \change_unchanged
 
 \end_layout

src/insets/InsetLayout.cpp

@@ -41,7 +41,8 @@ InsetLayout::InsetLayout() :
 	passthru_(false), parbreakisnewline_(false), freespacing_(false), 
 	keepempty_(false), forceltr_(false), 
 	needprotect_(false), intoc_(false), spellcheck_(true), 
-	resetsfont_(false), display_(true), forcelocalfontswitch_(false)
+	resetsfont_(false), display_(true), forcelocalfontswitch_(false),
+	forceownlines_(false)
 {
 	labelfont_.setColor(Color_error);
 }