Fixed DFA for the last assignment / initialization in block. A relevant test. #KT-7599 Fixed.

compiler/testData/diagnostics/tests/smartCasts/variables/kt7599.kt

@@ -0,0 +1,23 @@
+trait A {
+    fun ok(): Boolean
+}
+
+class B: A {
+    override fun ok(): Boolean { return true }
+}
+
+class C: A {
+    override fun ok(): Boolean { return false }
+}
+
+fun foo(): Boolean {
+    var v: A
+    v = B()
+    // No smart cast needed, but not a problem if ever
+    if (<!DEBUG_INFO_SMARTCAST!>v<!>.ok()) {
+        v = C()
+    }
+    // No smart cast needed, and no smart cast possible!
+    // We cannot choose between B and C
+    return v.ok()
+}