Fix pytrace=False and --tb=line reports None (#10905)

Closes #10831.

This fixes a small bug where running tests that contained
`pytest.fail(pytrace=False)` with the `--tb=line` flag set results in
 an output of "None" in the Failures section of the output, and adds
 a test to ensure the behavior is correct.

testing/test_terminal.py

@@ -1539,6 +1539,19 @@ class TestGenericReporting:
         s = result.stdout.str()
         assert "def test_func2" not in s
 
+    def test_tb_crashline_pytrace_false(self, pytester: Pytester, option) -> None:
+        p = pytester.makepyfile(
+            """
+            import pytest
+            def test_func1():
+                pytest.fail('test_func1', pytrace=False)
+        """
+        )
+        result = pytester.runpytest("--tb=line")
+        result.stdout.str()
+        bn = p.name
+        result.stdout.fnmatch_lines(["*%s:3: Failed: test_func1" % bn])
+
     def test_pytest_report_header(self, pytester: Pytester, option) -> None:
         pytester.makeconftest(
             """