Remove PAD_PROBE_ID_INVALID and Default impls for PadProbeId and NotifyWatchId

These should never ever be 0, and passing 0 to any of the functions
using them will result in assertions.

gstreamer/src/element.rs

@@ -65,7 +65,7 @@ pub enum ElementMessageType {
     Info,
 }
 
-#[derive(Debug, Default, PartialEq, Eq)]
+#[derive(Debug, PartialEq, Eq)]
 pub struct NotifyWatchId(libc::c_ulong);
 
 impl ToGlib for NotifyWatchId {
@@ -79,6 +79,7 @@ impl ToGlib for NotifyWatchId {
 impl FromGlib<libc::c_ulong> for NotifyWatchId {
     fn from_glib(val: libc::c_ulong) -> NotifyWatchId {
         skip_assert_initialized!();
+        assert_ne!(val, 0);
         NotifyWatchId(val)
     }
 }

gstreamer/src/lib.rs

@@ -115,7 +115,7 @@ pub use element::{ElementExtManual, ElementMessageType, NotifyWatchId};
 pub use element::{ELEMENT_METADATA_AUTHOR, ELEMENT_METADATA_DESCRIPTION, ELEMENT_METADATA_DOC_URI,
                   ELEMENT_METADATA_ICON_NAME, ELEMENT_METADATA_KLASS, ELEMENT_METADATA_LONGNAME};
 pub use bin::BinExtManual;
-pub use pad::{PadExtManual, PadProbeData, PadProbeId, PadProbeInfo, PAD_PROBE_ID_INVALID};
+pub use pad::{PadExtManual, PadProbeData, PadProbeId, PadProbeInfo};
 pub use gobject::GObjectExtManualGst;
 pub use child_proxy::ChildProxyExtManual;
 pub use tag_setter::TagSetterExtManual;

gstreamer/src/pad.rs

@@ -56,9 +56,8 @@ impl Pad {
     }
 }
 
-#[derive(Debug, Default, PartialEq, Eq)]
+#[derive(Debug, PartialEq, Eq)]
 pub struct PadProbeId(libc::c_ulong);
-pub const PAD_PROBE_ID_INVALID: PadProbeId = PadProbeId(0);
 
 impl ToGlib for PadProbeId {
     type GlibType = libc::c_ulong;
@@ -71,6 +70,7 @@ impl ToGlib for PadProbeId {
 impl FromGlib<libc::c_ulong> for PadProbeId {
     fn from_glib(val: libc::c_ulong) -> PadProbeId {
         skip_assert_initialized!();
+        assert_ne!(val, 0);
         PadProbeId(val)
     }
 }