fix postpolicy condition key check (#1154)

Author: joke-lee

api/src/main/java/io/minio/PostPolicy.java

@@ -189,7 +189,7 @@ public Map<String, String> formData(@Nonnull Credentials creds, @Nonnull String
       throw new IllegalArgumentException("region cannot be empty");
     }
 
-    if (!conditions.get(EQ).containsKey("key") && conditions.get(STARTS_WITH).containsKey("key")) {
+    if (!conditions.get(EQ).containsKey("key") && !conditions.get(STARTS_WITH).containsKey("key")) {
       throw new IllegalArgumentException("key condition must be set");
     }