Fix --most-allocations with the value of 0

In the docs we say that a value of 0 will show all entries but
currently the plugin crashes because it interprets the value of 0 as a
string and is not properly propagated to show all entries.

src/pytest_memray/plugin.py

@@ -287,6 +287,8 @@ def pytest_terminal_summary(
         )
 
         max_results = cast(int, value_or_ini(self.config, "most_allocations"))
+        if max_results == 0:
+            max_results = len(total_sizes)
 
         for test_id, total_size in total_sizes.most_common(max_results):
             result = self.results[test_id]

src/pytest_memray/utils.py

@@ -48,7 +48,7 @@ def parse_memory_string(mem_str: str) -> float:
 
 def value_or_ini(config: Config, key: str) -> object:
     value = config.getvalue(key)
-    if value:
+    if value is not None:
         return value
     try:
         return config.getini(key)

tests/test_pytest_memray.py

@@ -373,6 +373,39 @@ def test_bar():
     assert "results for test_memray_report_limit.py::test_bar" in output
 
 
+def test_memray_report_limit_without_limit(pytester: Pytester) -> None:
+    pytester.makepyfile(
+        """
+        import pytest
+        from memray._test import MemoryAllocator
+        allocator = MemoryAllocator()
+
+        def allocating_func1():
+            allocator.valloc(1024)
+            allocator.free()
+
+        def allocating_func2():
+            allocator.valloc(1024*2)
+            allocator.free()
+
+        def test_foo():
+            allocating_func1()
+
+        def test_bar():
+            allocating_func2()
+    """
+    )
+
+    result = pytester.runpytest("--memray", "--most-allocations=0")
+
+    assert result.ret == ExitCode.OK
+
+    output = result.stdout.str()
+
+    assert "results for test_memray_report_limit_without_limit.py::test_foo" in output
+    assert "results for test_memray_report_limit_without_limit.py::test_bar" in output
+
+
 def test_failing_tests_are_not_reported(pytester: Pytester) -> None:
     pytester.makepyfile(
         """