Print errors while reloading externally edited files

These exceptions were silently dropped, which is pretty much never a
good idea.

app/src/processing/app/Base.java

@@ -614,7 +614,7 @@ public class Base {
           activeEditor.getCurrentTab().getTextArea().setCaretPosition(previousCaretPosition);
         }
       } catch (IOException e) {
-        // noop
+        System.err.println(e);
       }
     }