fix: address CodeRabbit review issues for Billing Programs API

- Add error logging and status messages to empty catch blocks in AlternativeBillingScreen.kt
- Fix exception propagation in OpenIapModule.kt Proxy handler using resumeWithException()
- Add null-safe activity handling to prevent potential NPE

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: hyochan

packages/google/Example/src/main/java/dev/hyo/martie/screens/AlternativeBillingScreen.kt

@@ -638,8 +638,17 @@ fun AlternativeBillingScreen(navController: NavController) {
                                                 }
 
                                                 // Step 2: Launch external link
+                                                val currentActivity = activity
+                                                if (currentActivity == null) {
+                                                    iapStore.postStatusMessage(
+                                                        "Activity not available",
+                                                        PurchaseResultStatus.Error
+                                                    )
+                                                    return@launch
+                                                }
+
                                                 val launched = iapStore.launchExternalLink(
-                                                    activity!!,
+                                                    currentActivity,
                                                     LaunchExternalLinkParamsAndroid(
                                                         billingProgram = selectedBillingProgram,
                                                         launchMode = ExternalLinkLaunchModeAndroid.LaunchInExternalBrowserOrApp,
@@ -745,7 +754,11 @@ fun AlternativeBillingScreen(navController: NavController) {
                                                     )
                                                 }
                                             } catch (e: Exception) {
-                                                // Error handled by store
+                                                android.util.Log.e("AlternativeBilling", "Legacy alternative billing error: ${e.message}", e)
+                                                iapStore.postStatusMessage(
+                                                    "Alternative billing failed: ${e.message}",
+                                                    PurchaseResultStatus.Error
+                                                )
                                             }
                                         }
                                     },
@@ -791,7 +804,11 @@ fun AlternativeBillingScreen(navController: NavController) {
                                                 // If user selects Google Play → onPurchaseUpdated callback
                                                 // If user selects alternative → UserChoiceBillingListener callback
                                             } catch (e: Exception) {
-                                                // Error handled by store
+                                                android.util.Log.e("AlternativeBilling", "User choice billing error: ${e.message}", e)
+                                                iapStore.postStatusMessage(
+                                                    "User choice billing failed: ${e.message}",
+                                                    PurchaseResultStatus.Error
+                                                )
                                             }
                                         }
                                     },

packages/google/openiap/src/play/java/dev/hyo/openiap/OpenIapModule.kt

@@ -68,6 +68,7 @@ import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.suspendCancellableCoroutine
 import kotlinx.coroutines.withContext
 import kotlin.coroutines.resume
+import kotlin.coroutines.resumeWithException
 import java.lang.ref.WeakReference
 
 // AlternativeBillingMode moved to main source set (shared between Play and Horizon)
@@ -515,15 +516,15 @@ class OpenIapModule(
                                         externalTransactionToken = token
                                     ))
                                 } else if (continuation.isActive) {
-                                    throw OpenIapError.PurchaseFailed
+                                    continuation.resumeWithException(OpenIapError.PurchaseFailed)
                                 }
                             } catch (e: Exception) {
                                 OpenIapLog.e("Failed to extract token: ${e.message}", e, TAG)
-                                if (continuation.isActive) throw OpenIapError.PurchaseFailed
+                                if (continuation.isActive) continuation.resumeWithException(OpenIapError.PurchaseFailed)
                             }
                         } else {
                             OpenIapLog.e("Reporting details creation failed: ${result?.debugMessage}", tag = TAG)
-                            if (continuation.isActive) throw OpenIapError.PurchaseFailed
+                            if (continuation.isActive) continuation.resumeWithException(OpenIapError.PurchaseFailed)
                         }
                     }
                     null