video: Handle Result returned by VideoMeta::add()

By simply unwrapping for now, which is still better silently having no
VideoMeta.

video/closedcaption/src/cea608overlay.rs

@@ -186,7 +186,8 @@ impl Cea608Overlay {
             gst_video::VideoFormat::Argb,
             width as u32,
             height as u32,
-        );
+        )
+        .unwrap();
         let buffer = buffer.into_mapped_buffer_writable().unwrap();
         let buffer = {
             let buffer_ptr = unsafe { buffer.get_buffer().as_ptr() };

video/dav1d/src/dav1ddec.rs

@@ -235,7 +235,8 @@ impl Dav1dDec {
                 info.height(),
                 &offsets,
                 &strides[..],
-            );
+            )
+            .unwrap();
         }
 
         let duration = pic.duration() as u64;