test: no longer fail on incorrect filters

When the filter doesn't (always) return a boolean or a number (to filter
by index), then we no longer want to fail. Instead, we want to provide a
list of all the elements that did match the filter expression.

So, when the filter does not even evaluate to a boolean value, then we
want to product an empty list.

And, if the filter sometimes evaluates to a boolean value and sometimes
doesn't, then we want a list of those values for which the filter did
evaluate to the boolean `true`.

As both these cases are very similar, it makes sense to combine them
into a single test.

Co-authored-by: berkaycanbc <berkay.can@camunda.com>
Co-authored-by: Nicola Puppa <nicola.puppa@camunda.com>
Co-authored-by: Remco Westerhoud <remco@westerhoud.nl>

src/test/scala/org/camunda/feel/impl/interpreter/InterpreterListExpressionTest.scala

@@ -260,15 +260,12 @@ class InterpreterListExpressionTest
       ValNumber(1))
   }
 
-  it should "fail if the filter doesn't return a boolean or a number" in {
+  it should "be filtered if the filter doesn't always return a boolean or a number" in {
     eval(""" [1,2,3,4]["not a valid filter"] """) should be (
-      ValError("Expected boolean filter or number but found 'ValString(not a valid filter)'")
+      ValList(List())
     )
-  }
-
-  it should "fail if the filter doesn't return always a boolean" in {
     eval("[1,2,3,4][if item < 3 then true else null]") should be (
-      ValError("expected Boolean but found 'ValNull'")
+      ValList(List(ValNumber(1), ValNumber(2)))
     )
   }