KT-3639 Can't find sources of AbstractIterator when navigating from stack strace

#KT-3639 fixed

idea/testData/filters/exceptionFilter/librarySources/dummy.txt

@@ -0,0 +1 @@
+This test doesn't have sources, but IDEA test framework needs sources dir

idea/testData/filters/exceptionFilter/mockLibrary/lib.kt

@@ -0,0 +1,10 @@
+package test
+
+class Foo {
+    fun member() {
+    }
+}
+
+fun foo() {
+    println()
+}

idea/testData/filters/exceptionFilter/mockLibrary/other.kt

@@ -0,0 +1,5 @@
+package test
+
+fun other() {
+    println("")
+}