Make LowPassFilter strict

Summary: Per title.

Reviewed By: danielbuechele

Differential Revision: D17073163

fbshipit-source-id: 08127d85af317ff701f4d131fd41df095f50f6a4

src/utils/LowPassFilter.tsx

@@ -24,7 +24,15 @@ export default class LowPassFilter {
     let removed: number = 0;
 
     if (this.hasFullBuffer()) {
-      removed = this.buffer.shift();
+      const tmp: number | undefined = this.buffer.shift();
+
+      if (tmp === undefined) {
+        throw new Error(
+          'Invariant violation: Buffer reported full but shift returned nothing.',
+        );
+      }
+
+      removed = tmp;
     }
 
     this.buffer.push(value);