Clear the sign lines before reloading

Wasn't reported yet, but if someone removed a line from the sign the old
one would still show up as we didn't clear the lines before reloading.

src/main/java/com/graywolf336/jail/listeners/CellSignListener.java

@@ -160,6 +160,12 @@ public class CellSignListener implements Listener {
     public void handleSignLineUpdates(JailPluginReloadedEvent event) {
         List<String> lines = pl.getConfig().getStringList(Settings.CELLSIGNLINES.getPath());
         
+        //Reset the lines to nothing
+        lineOne = "";
+        lineTwo = "";
+        lineThree = "";
+        lineFour = "";
+        
         if(lines.size() >= 1) lineOne = lines.get(0);
         if(lines.size() >= 2) lineTwo = lines.get(1);
         if(lines.size() >= 3) lineThree = lines.get(2);