Stop raising AttributeError when accessing missing calibration (Qiski…

…t#9681)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

qiskit/transpiler/target.py

@@ -81,6 +81,8 @@ def __init__(
     @property
     def calibration(self):
         """The pulse representation of the instruction."""
+        if self._calibration is None:
+            return None
         return self._calibration.get_schedule()
 
     @calibration.setter

releasenotes/notes/fix-missing-instproperty-calibration-e578052819592a0b.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Getting empty calibration from :class:`.InstructionProperties` raises
+    AttributeError has been fixed. Now it returns ``None``.

test/python/transpiler/test_target.py

@@ -1259,6 +1259,13 @@ def test_default_instmap_has_no_custom_gate(self):
         inst_map = target.instruction_schedule_map()
         self.assertFalse(inst_map.has_custom_gate())
 
+    def test_get_empty_target_calibration(self):
+        target = Target()
+        properties = {(0,): InstructionProperties(duration=100, error=0.1)}
+        target.add_instruction(XGate(), properties)
+
+        self.assertIsNone(target["x"][(0,)].calibration)
+
 
 class TestGlobalVariableWidthOperations(QiskitTestCase):
     def setUp(self):