fix completion not launching insert handler after explicit common prefix insertion

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

@@ -0,0 +1,5 @@
+public class SomeClass {
+  void foo(String param) {
+    if (param.<caret>)
+  }
+}

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

@@ -0,0 +1,5 @@
+public class SomeClass {
+  void foo(String param) {
+    if (param.equals(<caret>))
+  }
+}