ecore_timer: fix the default return value.

When this function fails to get the interval value, it should return -1.0.
Currently, the value can be integer(-1.0 has an Error).
Maybe it should be fixed.

@fix

src/lib/ecore/ecore_timer.eo

@@ -19,7 +19,7 @@ class Ecore.Timer (Eo.Base)
             /*@ Get the interval the timer ticks on. */
          }
          values {
-            double in; /*@ The new interval in seconds */
+            double in(-1); /*@ The new interval in seconds */
          }
       }
       pending {