added empty string case

Sources/Internal/RCBitCoder.swift

@@ -41,6 +41,9 @@ extension RCBitCoder {
     guard message.count <= configuration.maxMessageCount else {
       throw RCError.longText
     }
+    guard !message.isEmpty else {
+      return [RCBit](repeating: .zero, count: configuration.version.maxBitesPerSection * 4)
+    }
     //mapping into character indexes
     var indexes = message.map({configuration.characters.firstIndex(of: $0)!})
     //adding staring character index and filling with special indexes

Sources/Public/RCCoder.swift

@@ -38,7 +38,7 @@ public extension RCCoder {
   func encode(_ image: RCImage) throws -> UIImage {
     let bits = try bitCoder.encode(message: image.message)
     let image = imageEncoder.encode(image, bits: bits)
-    return UIImage()
+    return image
   }
   
   func decode(_ image: UIImage) throws -> String {