Better metastore close in mypyc test logic (#21250)

Author: hauntsaninja

mypyc/test/test_run.py

@@ -278,6 +278,7 @@ def run_case_step(self, testcase: DataDrivenTestCase, incremental_step: int) ->
         librt = has_test_name_tag(testcase.name, "librt")
         # Enable experimental features (local librt build also includes experimental features)
         experimental_features = has_test_name_tag(testcase.name, "experimental")
+        result = None
         try:
             compiler_options = CompilerOptions(
                 multi_file=self.multi_file,
@@ -313,7 +314,8 @@ def run_case_step(self, testcase: DataDrivenTestCase, incremental_step: int) ->
                 print(fix_native_line_number(line, testcase.file, testcase.line))
             assert False, "Compile error"
         finally:
-            result.manager.metastore.close()
+            if result is not None:
+                result.manager.metastore.close()
 
         # Check that serialization works on this IR. (Only on the first
         # step because the returned ir only includes updated code.)