Fix NPE in KnownVersioningSchemes#fromPurlType (#270)

Author: nscuro

versatile-core/src/main/java/io/github/nscuro/versatile/version/KnownVersioningSchemes.java

@@ -102,7 +102,7 @@ public static Optional<String> fromPurlType(final String purlType) {
             case "nuget" -> Optional.of(SCHEME_NUGET);
             case "pypi" -> Optional.of(SCHEME_PYPI);
             case "rpm" -> Optional.of(SCHEME_RPM);
-            default -> Optional.empty();
+            case null, default -> Optional.empty();
         };
     }
 

versatile-core/src/test/java/io/github/nscuro/versatile/version/KnownVersioningSchemesTest.java

@@ -57,4 +57,14 @@ void shouldReturnEmptyOptionalForUnknown() {
 
     }
 
+    @Nested
+    class FromPurlTypeTest {
+
+        @Test
+        void shouldReturnEmptyOptionalForNull() {
+            assertThat(KnownVersioningSchemes.fromPurlType(null)).isEmpty();
+        }
+
+    }
+
 }