mod(pane) example layout pane has top and bottom empty row

Fix corresponding RawText line control (i.e. last line and changes to
the window size in regards to the current line).

src/layout/Pane.zig

@@ -54,10 +54,9 @@ pub fn Layout(comptime Event: type) type {
         }
 
         pub fn content(this: *@This()) !*std.ArrayList(u8) {
-            const widget_content = try this.widget.content();
             this.c.clearRetainingCapacity();
             try this.c.appendSlice("\n");
-            try this.c.appendSlice(widget_content);
+            try this.c.appendSlice(try this.widget.content());
             try this.c.appendSlice("\n");
             return &this.c;
         }