Moved the check of negative flags for hydro pairs to the debug code. That...

Moved the check of negative flags for hydro pairs to the debug code. That never happens in real life code.

src/scheduler.c

@@ -1306,15 +1306,15 @@ void scheduler_reweight(struct scheduler *s, int verbose) {
 
       case task_type_sub_pair:
         if (t->ci->nodeID != nodeID || t->cj->nodeID != nodeID) {
-          if (t->flags < 0)
-            cost = 3.f * (wscale * count_i) * count_j;
-          else
-            cost = 3.f * (wscale * count_i) * count_j * sid_scale[t->flags];
+#ifdef SWIFT_DEBUG_CHECKS
+          if (t->flags < 0) error("Negative flag value!");
+#endif
+	  cost = 3.f * (wscale * count_i) * count_j * sid_scale[t->flags];
         } else {
-          if (t->flags < 0)
-            cost = 2.f * (wscale * count_i) * count_j;
-          else
-            cost = 2.f * (wscale * count_i) * count_j * sid_scale[t->flags];
+#ifdef SWIFT_DEBUG_CHECKS
+          if (t->flags < 0) error("Negative flag value!");
+#endif
+	  cost = 2.f * (wscale * count_i) * count_j * sid_scale[t->flags];
         }
         break;