FIXUP: Avoid crash when user may have modified conn/dupe tags

Signed-off-by: Taylor Smock <taylor.smock@kaart.com>

src/main/java/org/openstreetmap/josm/plugins/mapwithai/backend/commands/conflation/AbstractConflationCommand.java

@@ -100,10 +100,17 @@ public abstract class AbstractConflationCommand extends Command {
         final OsmPrimitive[] primitiveConnections = new OsmPrimitive[connections.length];
         for (int i = 0; i < connections.length; i++) {
             final String member = connections[i];
-            SimplePrimitiveId primitiveId = SimplePrimitiveId.fromString(member);
-            primitiveConnections[i] = dataSet.getPrimitiveById(primitiveId);
-            if (primitiveConnections[i] == null) {
-                missingPrimitives.put(i, new Pair<>(primitiveId.getUniqueId(), primitiveId.getType()));
+            try {
+                SimplePrimitiveId primitiveId = SimplePrimitiveId.fromString(member);
+                primitiveConnections[i] = dataSet.getPrimitiveById(primitiveId);
+                if (primitiveConnections[i] == null) {
+                    missingPrimitives.put(i, new Pair<>(primitiveId.getUniqueId(), primitiveId.getType()));
+                }
+            } catch (IllegalArgumentException e) {
+                // Assume someone fiddled with the tag if the pattern doesn't match.
+                if (!e.getMessage().contains("n|node|w|way|r|rel|relation")) {
+                    throw e;
+                }
             }
         }
         obtainMissingPrimitives(dataSet, primitiveConnections, missingPrimitives);

test/unit/org/openstreetmap/josm/plugins/mapwithai/commands/conflation/AbstractConflationCommandTest.java

@@ -0,0 +1,19 @@
+// License: GPL. For details, see LICENSE file.
+package org.openstreetmap.josm.plugins.mapwithai.commands.conflation;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
+import org.junit.jupiter.api.Test;
+import org.openstreetmap.josm.data.osm.DataSet;
+import org.openstreetmap.josm.plugins.mapwithai.backend.commands.conflation.AbstractConflationCommand;
+
+public class AbstractConflationCommandTest {
+    /**
+     * Non-regression test for
+     * <a href="https://josm.openstreetmap.de/ticket/19495">#19495</a>
+     */
+    @Test
+    public void testBadPrimitive() {
+        assertDoesNotThrow(() -> AbstractConflationCommand.getPrimitives(new DataSet(), "Linie 401699530"));
+    }
+}