always leave iReturnValues on the stack, even on error, so error handling can just log the error and continue as if nil was actually returned

stepmania/src/LuaManager.cpp

@@ -509,6 +509,8 @@ bool LuaHelpers::RunScript( Lua *L, const RString &sScript, const RString &sName
 		if( ret )
 		{
 			LuaHelpers::Pop( L, sError );
+			for( int i = 0; i < iReturnValues; ++i )
+				lua_pushnil( L );
 			return false;
 		}
 	}
@@ -519,6 +521,8 @@ bool LuaHelpers::RunScript( Lua *L, const RString &sScript, const RString &sName
 		if( ret )
 		{
 			LuaHelpers::Pop( L, sError );
+			for( int i = 0; i < iReturnValues; ++i )
+				lua_pushnil( L );
 			return false;
 		}
 	}
@@ -544,11 +548,7 @@ bool LuaHelpers::RunExpression( Lua *L, const RString &sExpression, const RStrin
 {
 	RString sFullExpression = "return " + sExpression;
 
-	bool bSuccess = LuaHelpers::RunScript( L, sFullExpression, sName, 1 );
-	if( !bSuccess )
-		lua_pushnil( L );
-
-	return bSuccess;
+	return LuaHelpers::RunScript( L, sFullExpression, sName, 1 );
 }
 
 bool LuaHelpers::RunExpressionB( const RString &str )

stepmania/src/LuaManager.h

@@ -48,8 +48,9 @@ private:
 
 namespace LuaHelpers
 {
-	/* Run a script with the given name.  Return values are left on the Lua stack.
-	 * Returns false on error, with sError set. */
+	/* Run a script with the given name.  The given number of return values are left on
+	 * the Lua stack.  On error, nils are left on the stack, sError is set and 
+	 * false is returned. */
 	bool RunScript( Lua *L, const RString &sScript, const RString &sName, RString &sError, int iReturnValues = 0 );
 
 	/* Convenience: run a script with one return value, displaying an error on failure.