checking if stacktrace exists before accessing it (#594)

Author: MLDimitry

android/src/main/java/io/sentry/RNSentryModule.java

@@ -265,14 +265,16 @@ public void captureEvent(ReadableMap event) {
         if (event.hasKey("exception")) {
             ReadableNativeArray exceptionValues = (ReadableNativeArray)event.getMap("exception").getArray("values");
             ReadableNativeMap exception = exceptionValues.getMap(0);
-            ReadableNativeMap stacktrace = exception.getMap("stacktrace");
-            ReadableNativeArray frames = (ReadableNativeArray)stacktrace.getArray("frames");
-            if (exception.hasKey("value")) {
-                addExceptionInterface(eventBuilder, exception.getString("type"), exception.getString("value"), frames);
-            } else {
-                // We use type/type here since this indicates an Unhandled Promise Rejection
-                // https://github.com/getsentry/react-native-sentry/issues/353
-                addExceptionInterface(eventBuilder, exception.getString("type"), exception.getString("type"), frames);
+            if (exception.hasKey("stacktrace")) {
+                ReadableNativeMap stacktrace = exception.getMap("stacktrace");
+                ReadableNativeArray frames = (ReadableNativeArray)stacktrace.getArray("frames");
+                if (exception.hasKey("value")) {
+                    addExceptionInterface(eventBuilder, exception.getString("type"), exception.getString("value"), frames);
+                } else {
+                    // We use type/type here since this indicates an Unhandled Promise Rejection
+                    // https://github.com/getsentry/react-native-sentry/issues/353
+                    addExceptionInterface(eventBuilder, exception.getString("type"), exception.getString("type"), frames);
+                }
             }
         }