Swallow all validator exceptions

so the LSP server does not terminate when an exception is thrown during validation. Usually exceptions are only thrown, when the model is not well-formed, which will either be a syntactical error (will be displayed on the client), or another validation rule will find it. In either case, we can safely ignore all exceptions.

subprojects/oxsts.lang/src/main/java/hu/bme/mit/semantifyr/oxsts/lang/validation/OxstsValidator.java

@@ -20,6 +20,11 @@ public class OxstsValidator extends AbstractOxstsValidator {
 	public static final String INVALID_INLINING = "invalidInlining";
 	public static final String INVALID_MULTIPLICITIY = "invalidMultiplicity";
 
+    @Override
+    protected void handleExceptionDuringValidation(Throwable targetException) throws RuntimeException {
+        // swallow all exceptions!
+    }
+
     @Check
     public void checkFeatureSubsetting(Feature feature) {
         if (feature.getSubsets().isEmpty()) return;