Compatibility between legacy script and special backgrounds

git-svn-id: http://svn.berlios.de/svnroot/repos/oolite-linux/trunk@5382 127b21dd-08f5-0310-b4b7-95ae10353056

src/Core/Entities/PlayerEntityLegacyScriptEngine.m

@@ -2385,6 +2385,10 @@ static int scriptRandomSeed = -1;	// ensure proper random function
 
 - (void) setGuiToMissionScreen
 {
+	// reset special background as legacy scripts can't use it, and this
+	// is only called by legacy scripts
+	[self setMissionBackgroundSpecial:nil];
+
 	[self setGuiToMissionScreenWithCallback:NO];
 }