Handle missing units without failure.

Still need to deal with multiple perf data in a single line (not sure if
it's technically correct at all).

mnpw/nagios.py

@@ -50,12 +50,12 @@ def parse_perf_data(line):  # noqa: MC0001
         for i in range(len(value) - 1, 0, -1):
             if value[i].isdigit():
                 break
-        value, unit = (
+        pd["value"], pd["unit"] = (
             float(value[: i + 1]),
             value[i + 1 :],  # noqa: E203
         )
-    pd["value"] = value
-    pd["unit"] = unit
+    else:
+        pd["value"] = float(value)
 
     # Get the remaining fields, if available.
     try:

tests/test_nagios.py

@@ -119,8 +119,7 @@ def test_data_perf(line):
     assert isinstance(pd.name, str)
     assert len(pd.name) > 0
     assert isinstance(pd.value, float)
-    assert isinstance(pd.unit, str)
-    assert len(pd.unit) > 0
+    assert isinstance(pd.unit, (str, type(None)))
     assert isinstance(pd.warning, (float, type(None)))
     assert isinstance(pd.critical, (float, type(None)))
     assert isinstance(pd.min, (float, type(None)))