[FIR2IR] Fix generating body for for-loop

compiler/testData/codegen/box/fir/noSymbolForIntRangeIterator.kt

@@ -0,0 +1,34 @@
+// TARGET_BACKEND: JVM_IR
+// DUMP_IR
+// WITH_STDLIB
+
+var result = 0
+
+fun takeString(s: String) {
+    s.split("\n").forEach {
+        result += it.toIntOrNull() ?: 0
+    }
+}
+
+fun test() {
+    val x = 10
+    val y = 10
+
+    fun localFunc() {
+        for (i in 0..x) {
+            val s = buildString {
+                for (j in 0..y) {
+                    appendLine("${i * j}")
+                }
+            }
+            takeString(s)
+        }
+    }
+
+    localFunc()
+}
+
+fun box(): String {
+    test()
+    return if (result == 3025) "OK" else "Fail: $result"
+}