Fix zero-length AID handling in C4 tag parsing (issue #392)

library/src/main/java/pro/javacard/gp/GPRegistry.java

@@ -199,7 +199,12 @@ private void populate_tags(byte[] data, Kind type) throws GPDataException {
 
                 BerTlv loadfiletag = t.find(new BerTag(0xC4));
                 if (loadfiletag != null) {
-                    e.setLoadFile(new AID(loadfiletag.getBytesValue()));
+                    byte[] loadfileBytes = loadfiletag.getBytesValue();
+                    if (loadfileBytes.length > 0) {
+                        e.setLoadFile(new AID(loadfileBytes));
+                    } else {
+                        logger.warn("Skipping invalid load file AID (length: {})", loadfileBytes.length);
+                    }
                 }
                 BerTlv versiontag = t.find(new BerTag(0xCE));
                 if (versiontag != null) {

library/src/test/java/pro/javacard/gp/TestIssue392Fix.java

@@ -0,0 +1,38 @@
+package pro.javacard.gp;
+
+import apdu4j.core.HexUtils;
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+public class TestIssue392Fix {
+
+    @Test
+    public void testZeroLengthLoadFileAIDHandling() throws Exception {
+        // Test data with zero-length C4 tag (load file AID) as reported in issue #392
+        // E3 23 - Tag E3, length 23 (35 bytes)
+        // 4F 08 A000000003000000 - Tag 4F (main AID), length 8
+        // 9F70 01 01 - Tag 9F70 (lifecycle), length 1, data 01
+        // C5 03 9EFE80 - Tag C5 (privileges), length 3
+        // C4 00 - Tag C4 (load file AID), length 0 (this would cause IllegalArgumentException)
+        // CE 02 0000 - Tag CE (version), length 2
+        // CC 08 A000000003000000 - Tag CC (domain AID), length 8
+        byte[] data = HexUtils.hex2bin("E3234F08A0000000030000009F700101C5039EFE80C400CE020000CC08A000000003000000");
+
+        GPRegistry reg = new GPRegistry();
+
+        // This should not throw IllegalArgumentException: "AID must be between 5 and 16 bytes: 0"
+        // Instead it should gracefully handle the zero-length AID and continue parsing
+        reg.parse_and_populate(0x40, data, GPRegistryEntry.Kind.Application, GPCardProfile.defaultProfile());
+
+        // Verify that the registry has the entry (the parsing succeeded)
+        Assert.assertEquals(1, reg.allAIDs().size());
+        GPRegistryEntry entry = reg.iterator().next();
+
+        // Verify main properties are set correctly
+        Assert.assertEquals("A000000003000000", entry.getAID().toString());
+        Assert.assertEquals(1, entry.getLifeCycle());
+
+        // Verify the zero-length load file AID was handled gracefully (no source set)
+        Assert.assertFalse(entry.getSource().isPresent());
+    }
+}