Handle empty strings in sqlcommenter (#3309)

* Handle empty strings

Safer check for a trailing semicolon that could handle
empty strings as well.

* Updated CHANGELOG.md

* Test for empty SQL strings in sqlcommenter

---------

Co-authored-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>

instrumentation/opentelemetry-instrumentation-django/tests/test_sqlcommenter.py

@@ -146,3 +146,31 @@ class TestMiddleware(WsgiTestBase):
 
         # check if query_wrapper is added to the context for 2 databases
         self.assertEqual(query_wrapper.call_count, 2)
+
+    @patch(
+        "opentelemetry.instrumentation.django.middleware.sqlcommenter_middleware._get_opentelemetry_values"
+    )
+    def test_empty_sql(self, trace_capture):
+        requests_mock = MagicMock()
+        requests_mock.resolver_match.view_name = "view"
+        requests_mock.resolver_match.route = "route"
+        requests_mock.resolver_match.app_name = "app"
+
+        trace_capture.return_value = {
+            "traceparent": "*traceparent='00-000000000000000000000000deadbeef-000000000000beef-00"
+        }
+        qw_instance = _QueryWrapper(requests_mock)
+        execute_mock_obj = MagicMock()
+        qw_instance(
+            execute_mock_obj,
+            "",
+            MagicMock("test"),
+            MagicMock("test1"),
+            MagicMock(),
+        )
+        output_sql = execute_mock_obj.call_args[0][0]
+        self.assertEqual(
+            output_sql,
+            " /*app_name='app',controller='view',route='route',traceparent='%%2Atraceparent%%3D%%2700-0000000"
+            "00000000000000000deadbeef-000000000000beef-00'*/",
+        )