Fix parsing of negative limits in Lauris parameters.

- VERBESSERUNG: Keine Fehlermeldung mehr, falls Referenzbereiche negative Werte enthalten (wie z.B. Base Excess) [#650db4d2]

Tests/Importer/ZaaImporter/LaurisItemTest.cs

@@ -29,6 +29,7 @@ namespace Tests.Importer.ZaaImporter
     class LaurisItemTest
     {
         [Test]
+        [TestCase("BE: 5.2 [-2 - 2] mmol/l", "BE", 5.2, "mmol/l", -2, 2, false)]
         [TestCase("Natrium: 139 [135 - 145] mmol/l", "Natrium", 139, "mmol/l", 135, 145, true)]
         [TestCase("Kalium: 5.2 [3.5 - 5] mmol/l", "Kalium", 5.2, "mmol/l", 3.5, 5, false)]
         public void ParseLaurisWithBothLimits(