Add an additional null check in BaseKeyframeAnimation (#2486)

Fixes #2483
diff --git a/lottie/src/main/java/com/airbnb/lottie/animation/keyframe/BaseKeyframeAnimation.java b/lottie/src/main/java/com/airbnb/lottie/animation/keyframe/BaseKeyframeAnimation.java
index 1f8ec20..5f94a92 100644
--- a/lottie/src/main/java/com/airbnb/lottie/animation/keyframe/BaseKeyframeAnimation.java
+++ b/lottie/src/main/java/com/airbnb/lottie/animation/keyframe/BaseKeyframeAnimation.java
@@ -112,7 +112,8 @@
     Keyframe<K> keyframe = getCurrentKeyframe();
     // Keyframe should not be null here but there seems to be a Xiaomi Android 10 specific crash.
     // https://github.com/airbnb/lottie-android/issues/2050
-    if (keyframe == null || keyframe.isStatic()) {
+    // https://github.com/airbnb/lottie-android/issues/2483
+    if (keyframe == null || keyframe.isStatic() || keyframe.interpolator == null) {
       return 0f;
     }
     //noinspection ConstantConditions