Add 'Add != null' quick fix.

pkg/analysis_server/test/services/correction/fix_test.dart

Index: pkg/analysis_server/test/services/correction/fix_test.dart
diff --git a/pkg/analysis_server/test/services/correction/fix_test.dart b/pkg/analysis_server/test/services/correction/fix_test.dart
index e501b42f5b67763806c300eac88ed3d603139ab9..2b6f848e331e4d2bcb0b35f996dadbd7eef5dfef 100644
--- a/pkg/analysis_server/test/services/correction/fix_test.dart
+++ b/pkg/analysis_server/test/services/correction/fix_test.dart
@@ -3097,6 +3097,25 @@ main(p) {
     }
   }
 
+  void test_nonBoolCondition_addNotNull() {
+    resolveTestUnit('''
+main(String p) {
+  if (p) {
+    print(p);
+  }
+}
+''');
+    assertHasFix(
+        DartFixKind.ADD_NE_NULL,
+        '''
+main(String p) {
+  if (p != null) {
+    print(p);
+  }
+}
+''');
+  }
+
   void test_removeDeadCode_condition() {
     resolveTestUnit('''
 main(int p) {