refactoring: fixed error message in VisualizerPlainText

src/main/java/pacmanGame/VisualizerPlainText.java

@@ -56,7 +56,7 @@ public class VisualizerPlainText implements Visualizer {
 					output += sprites.get(cell.type);	
 				}
 				else {
-					System.out.println("unknown type" + cell.type);
+					System.out.println("unknown type " + cell.type);
 				}
 			}	
 			output += "\n";