fix some empty stack exceptions during dfa analysis

java/java-tests/testData/codeInsight/completion/normal/OrAssignmentDfa.java

@@ -0,0 +1,17 @@
+class Foo {
+
+    boolean foo(Object o, final PairFunction<String, ElementType, Boolean> fun){
+        boolean result = true;
+        result |= fun.fun(path);
+        if (o instanceof String) {
+            o.subst<caret>
+        }
+    }
+
+    void foo(String s) {}
+}
+
+interface PairFunction<T, V, U> {
+  U fun(T t, V v);
+
+}

java/java-tests/testData/codeInsight/completion/normal/OrAssignmentDfa_after.java

@@ -0,0 +1,17 @@
+class Foo {
+
+    boolean foo(Object o, final PairFunction<String, ElementType, Boolean> fun){
+        boolean result = true;
+        result |= fun.fun(path);
+        if (o instanceof String) {
+            ((String) o).substring(<caret>)
+        }
+    }
+
+    void foo(String s) {}
+}
+
+interface PairFunction<T, V, U> {
+  U fun(T t, V v);
+
+}

java/java-tests/testSrc/com/intellij/codeInsight/completion/NormalCompletionTest.groovy

@@ -809,6 +809,8 @@ public class NormalCompletionTest extends LightFixtureCompletionTestCase {
   public void testQualifierCastingWithUnknownAssignments() throws Throwable { doTest(); }
   public void testQualifierCastingBeforeLt() throws Throwable { doTest(); }
 
+  public void testOrAssignmentDfa() throws Throwable { doTest(); }
+
   public void testWildcardsInLookup() throws Exception {
     configure()
     assertNotNull(getLookup());