Properly handle seek bar input events.

src/org/thoughtcrime/securesms/audio/AudioSlidePlayer.java

@@ -246,12 +246,10 @@ public class AudioSlidePlayer implements SensorEventListener {
   }
 
   public synchronized void seekTo(double progress) throws IOException {
-    if (mediaPlayer == null) return;
-
-    if (isReady()) {
-      mediaPlayer.seekTo((long) (mediaPlayer.getDuration() * progress));
-    } else {
+    if (mediaPlayer == null || !isReady()) {
       play(progress);
+    } else {
+      mediaPlayer.seekTo((long) (mediaPlayer.getDuration() * progress));
     }
   }
 

src/org/thoughtcrime/securesms/loki/views/WaveformSeekBar.kt

@@ -249,9 +249,11 @@ class WaveformSeekBar : View {
                 if (abs(event.x - touchDownX) > scaledTouchSlop) {
                     updateProgress(event, false)
                 }
-
                 performClick()
             }
+            MotionEvent.ACTION_CANCEL -> {
+                userSeeking = false
+            }
         }
         return true
     }