Making sure we never have zero backing indices (elastic#130945)

Author: masseyke

x-pack/plugin/deprecation/src/test/java/org/elasticsearch/xpack/deprecation/DataStreamDeprecationCheckerTests.java

@@ -75,7 +75,7 @@ public void testOldIndicesCheck() {
 
     public void testOldIndicesCheckWithOnlyNewIndices() {
         // This tests what happens when any old indices that we have are closed. We expect no deprecation warning.
-        int newOpenIndexCount = randomIntBetween(0, 100);
+        int newOpenIndexCount = randomIntBetween(1, 100);
         int newClosedIndexCount = randomIntBetween(0, 100);
 
         Map<String, IndexMetadata> nameToIndexMetadata = new HashMap<>();