Guild PQ + fixed negative EXP error

Implemented Guild PQ. Fixed a problem introduced earlier where negative
EXP would be deemed as "integer overflow", provoking many game breaking
issues as result.

scripts/portal/guild1F00.js

@@ -22,10 +22,13 @@
 /*
 Return from Sharen III's Grave - Guild Quest
 
-@Author Lerk
+@Author Ronan
 */
 
 function enter(pi) {
-        pi.warp(990000600, 1);
+        var backPortals = [6, 8, 9, 11];
+        var idx = pi.getEventInstance().gridCheck(pi.getPlayer());
+        
+        pi.warp(990000600, backPortals[idx]);
         return true;
 }