Fix contact discovery refresh crash.

core-util/src/main/java/org/signal/core/util/concurrent/RxExtensions.kt

@@ -0,0 +1,26 @@
+@file:JvmName("RxExtensions")
+
+package org.signal.core.util.concurrent
+
+import io.reactivex.rxjava3.core.Single
+import java.lang.RuntimeException
+
+/**
+ * Throw an [InterruptedException] if a [Single.blockingGet] call is interrupted. This can
+ * happen when being called by code already within an Rx chain that is disposed.
+ *
+ * [Single.blockingGet] is considered harmful and should not be used.
+ */
+@Throws(InterruptedException::class)
+fun <T : Any> Single<T>.safeBlockingGet(): T {
+  try {
+    return blockingGet()
+  } catch (e: RuntimeException) {
+    val cause = e.cause
+    if (cause is InterruptedException) {
+      throw cause
+    } else {
+      throw e
+    }
+  }
+}