Fixed refcounting bug in new string implementation

qtools/qcstring.h

@@ -497,6 +497,8 @@ public:
           }
         }
         StringRep &operator=(const StringRep &s)
+        {
+          if (&s!=this)
           {
             if (!u.s.isShort)
             {
@@ -512,6 +514,7 @@ public:
               u.l.d = s.u.l.d;
               u.l.d->refCount++;
             }
+          }
           return *this;
         }
         StringRep &operator=(const char *str)