Ensure encrypted fields data exists fully (#1802)

Appears theres been a change when using mongocryptd and
an empty document is returned.

 Removed legacy Client Encryption test from the shell runner

JAVA-5959

Author: rozza

.evergreen/run-csfle-tests-with-mongocryptd.sh

@@ -60,8 +60,6 @@ echo "Running tests with Java ${JAVA_VERSION}"
       ${GRADLE_EXTRA_VARS} \
       -Dorg.mongodb.test.fle.on.demand.credential.test.failure.enabled=true \
       --stacktrace --info --continue \
-      driver-legacy:test \
-          --tests "*.Client*Encryption*" \
       driver-sync:test \
           --tests "*.Client*Encryption*" \
       driver-reactive-streams:test \

driver-core/src/main/com/mongodb/internal/operation/DropCollectionOperation.java

@@ -154,8 +154,8 @@ public void executeAsync(final AsyncWriteBinding binding, final SingleResultCall
      *
      * @return the list of commands to run to create the collection
      */
-    private List<Supplier<BsonDocument>> getCommands(final BsonDocument encryptedFields) {
-        if (encryptedFields == null) {
+    private List<Supplier<BsonDocument>> getCommands(@Nullable final BsonDocument encryptedFields) {
+        if (encryptedFields == null || encryptedFields.isEmpty()) {
             return singletonList(this::dropCollectionCommand);
         } else  {
             return asList(