add checks to make sure crash entries are not none where they should not be

src/_pytest/_code/code.py

@@ -650,13 +650,18 @@ class ExceptionInfo(Generic[E]):
             Added the ``chain`` parameter.
         """
         if style == "native":
+            r = self._getreprcrash()
+            if r is None:
+                raise ValueError(
+                    "There should always be a non-hidden traceback entry for the top level function."
+                )
             return ReprExceptionInfo(
                 reprtraceback=ReprTracebackNative(
                     traceback.format_exception(
                         self.type, self.value, self.traceback[0]._rawentry
                     )
                 ),
-                reprcrash=self._getreprcrash(),
+                reprcrash=r,
             )
 
         fmt = FormattedExcinfo(

src/_pytest/reports.py

@@ -347,6 +347,10 @@ class TestReport(BaseReport):
             elif isinstance(excinfo.value, skip.Exception):
                 outcome = "skipped"
                 r = excinfo._getreprcrash()
+                if r is None:
+                    raise ValueError(
+                        "There should always be a traceback entry for skipping a test."
+                    )
                 if excinfo.value._use_item_location:
                     path, line = item.reportinfo()[:2]
                     assert line is not None

testing/code/test_excinfo.py

@@ -294,6 +294,7 @@ class TestTraceback_f_g_h:
         excinfo = pytest.raises(ValueError, f)
         tb = excinfo.traceback
         entry = tb.getcrashentry()
+        assert entry is not None
         co = _pytest._code.Code.from_function(h)
         assert entry.frame.code.path == co.path
         assert entry.lineno == co.firstlineno + 1