fix #18620 (#18624)

* fix #18620

* add testcase

lib/system/excpt.nim

@@ -524,10 +524,7 @@ proc getStackTrace(e: ref Exception): string =
 proc getStackTraceEntries*(e: ref Exception): seq[StackTraceEntry] =
   ## Returns the attached stack trace to the exception `e` as
   ## a `seq`. This is not yet available for the JS backend.
-  when not defined(nimSeqsV2):
+  shallowCopy(result, e.trace)
-    shallowCopy(result, e.trace)
-  else:
-    result = move(e.trace)
 
 proc getStackTraceEntries*(): seq[StackTraceEntry] =
   ## Returns the stack trace entries for the current stack trace.

tests/exception/t18620.nim

@@ -0,0 +1,17 @@
+discard """
+  matrix: "--gc:arc; --gc:refc"
+"""
+
+proc hello() =
+  raise newException(ValueError, "You are wrong")
+
+var flag = false
+
+try:
+  hello()
+except ValueError as e:
+  flag = true
+  doAssert len(getStackTraceEntries(e)) > 0
+  doAssert len(getStackTraceEntries(e)) > 0
+
+doAssert flag