[FIR] Fix clearing info about DF variable after reassignment

compiler/fir/analysis-tests/testData/resolve/smartcasts/safeCalls/complexIfWithOr.kt

@@ -0,0 +1,13 @@
+interface State
+interface Complex {
+    val superClass: Complex?
+}
+
+interface ExceptionState : State
+
+fun test(qualifier: State?) {
+    if (qualifier == null || qualifier is ExceptionState || (qualifier as? Complex)?.superClass == null) {
+        return
+    }
+    qualifier.superClass
+}