Fix validateTags() bug

empty string array is a valid tag. TF 1.x model does not have any tags

Author: frankfliu

tensorflow-core/tensorflow-core-api/src/main/java/org/tensorflow/SavedModelBundle.java

@@ -429,7 +429,7 @@ opts, runOpts, new BytePointer(exportDir), new PointerPointer(tags),
   }
 
   private static void validateTags(String[] tags) {
-    if (tags == null || tags.length == 0 || Arrays.stream(tags).anyMatch(t -> t == null || t.isEmpty())) {
+    if (tags == null || Arrays.stream(tags).anyMatch(t -> t == null || t.isEmpty())) {
       throw new IllegalArgumentException("Invalid tags: " + Arrays.toString(tags));
     }
   }

tensorflow-core/tensorflow-core-api/src/test/java/org/tensorflow/SavedModelBundleTest.java

@@ -264,9 +264,6 @@ public void cannotExportOrImportInvalidTags() {
     assertThrows(IllegalArgumentException.class, () ->
         SavedModelBundle.loader("/").withTags()
     );
-    assertThrows(IllegalArgumentException.class, () ->
-        SavedModelBundle.loader("/").withTags(new String[]{})
-    );
     assertThrows(IllegalArgumentException.class, () ->
         SavedModelBundle.loader("/").withTags(new String[]{"tag", null})
     );
@@ -276,9 +273,6 @@ public void cannotExportOrImportInvalidTags() {
     assertThrows(IllegalArgumentException.class, () ->
         SavedModelBundle.exporter("/").withTags()
     );
-    assertThrows(IllegalArgumentException.class, () ->
-        SavedModelBundle.exporter("/").withTags(new String[]{})
-    );
     assertThrows(IllegalArgumentException.class, () ->
         SavedModelBundle.exporter("/").withTags(new String[]{"tag", null})
     );