Replace never occurring null branch with assertion

Author: mpkorstanje

junit-platform-engine/src/main/java/org/junit/platform/engine/support/store/NamespacedHierarchicalStore.java

@@ -567,11 +567,9 @@ void run() {
 				throw throwAsUncheckedException(e);
 			}
 			catch (ExecutionException e) {
-				Throwable t = e.getCause();
-				if (t == null) {
-					t = e;
-				}
-				UnrecoverableExceptions.rethrowIfUnrecoverable(t);
+				// non-null guaranteed by FutureTask
+				var cause = requireNonNull(e.getCause());
+				UnrecoverableExceptions.rethrowIfUnrecoverable(cause);
 				return null;
 			}
 		}
@@ -586,12 +584,10 @@ Object getOrThrow() {
 				throw throwAsUncheckedException(e);
 			}
 			catch (ExecutionException e) {
-				Throwable t = e.getCause();
-				if (t == null) {
-					t = e;
-				}
-				UnrecoverableExceptions.rethrowIfUnrecoverable(t);
-				throw throwAsUncheckedException(t);
+				// non-null guaranteed by FutureTask
+				var cause = requireNonNull(e.getCause());
+				UnrecoverableExceptions.rethrowIfUnrecoverable(cause);
+				throw throwAsUncheckedException(cause);
 			}
 		}
 	}