gui2/tgamestate_inspector: Don't skip pages with empty contents

Those are sometimes relevant (for example, empty WML variables or
containers/arrays). We don't want to conceal the truth here because this
is supposed to be a debugging aid.

changelog

@@ -112,6 +112,8 @@ Version 1.13.1+dev:
      messages involving macros.
    * Added WML menu item and event handler views to the Gamestate Inspector
      dialog.
+   * The Gamestate Inspector now displays empty WML variables too (including
+     containers/arrays).
    * Added new possibilities for [effect]:
      * apply_to=alignment - change a unit's alignment
      * apply_to=attacks_left - change a unit's attacks per turn

src/gui/dialogs/gamestate_inspector.cpp

@@ -191,6 +191,11 @@ public:
 
 	unsigned int get_num_page(const std::string& s)
 	{
+		// We always want to reserve a page for empty contents.
+		if(s.empty()) {
+			return 1;
+		}
+
 		return (s.length() / max_inspect_win_len) + (s.length() % max_inspect_win_len > 0 ? 1 : 0);
 	}
 };