fixed a minor bug that caused the statevector simulator to output a f…

…aulty global phase in some situtations

src/qrisp/simulator/tensor_factor.py

@@ -204,6 +204,8 @@ def multi_measure(self, mes_qubits, return_res_tf = True):
         return p_list, tf_list, outcome_index_list
 
     def disentangle(self, qubit):
+        if len(self.qubits) == 1:
+            return self, self
 
         # Swap the index that is supposed to be measured to the front
         index = self.qubits.index(qubit)