CBL-7610 : query collations should default to system locale instead of null (#444)

Author: Aniket392

common/main/java/com/couchbase/lite/Collation.java

@@ -124,7 +124,12 @@ protected Collation(boolean isUnicode, @Nullable String locale) {
 
     @NonNull
     protected Collation setLocale(@Nullable String locale) {
-        this.locale = locale;
+        // For Unicode collations, default to system locale when null is passed
+        if (isUnicode && locale == null) {
+            this.locale = System.getProperty("user.language");
+        } else {
+            this.locale = locale;
+        }
         return this;
     }
 

common/test/java/com/couchbase/lite/QueryTest.java

@@ -1944,19 +1944,19 @@ public void testGenerateJSONCollation() {
         expected.add(json2);
         Map<String, Object> json3 = new HashMap<>();
         json3.put("UNICODE", true);
-        json3.put("LOCALE", null);
+        json3.put("LOCALE", System.getProperty("user.language"));
         json3.put("CASE", true);
         json3.put("DIAC", true);
         expected.add(json3);
         Map<String, Object> json4 = new HashMap<>();
         json4.put("UNICODE", true);
-        json4.put("LOCALE", null);
+        json4.put("LOCALE", System.getProperty("user.language"));
         json4.put("CASE", false);
         json4.put("DIAC", true);
         expected.add(json4);
         Map<String, Object> json5 = new HashMap<>();
         json5.put("UNICODE", true);
-        json5.put("LOCALE", null);
+        json5.put("LOCALE", System.getProperty("user.language"));
         json5.put("CASE", false);
         json5.put("DIAC", false);
         expected.add(json5);