Do not overwrite existing status of UI event transactions

[romtsn]

Description

We should not force set the status when finishing UI event transactions, but instead check if the existing status is null and only set the status in that case, otherwise we might be overriding what the user set

sentry-java/sentry-android-core/src/main/java/io/sentry/android/core/internal/gestures/SentryGestureListener.java

Line 277 in 84f0ef1

activeTransaction.finish(status);

[romtsn]

@adinauer to check if this should also be done for backend integrations