do not suggest completions for empty dot target

pkg/analysis_server/lib/src/services/completion/optype.dart

Index: pkg/analysis_server/lib/src/services/completion/optype.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/optype.dart b/pkg/analysis_server/lib/src/services/completion/optype.dart
index 1ed85d523e6e7fd68e700924e793fdf7acbd165e..797d5a4bf7e735dd48ec8e9334b136e53b912746 100644
--- a/pkg/analysis_server/lib/src/services/completion/optype.dart
+++ b/pkg/analysis_server/lib/src/services/completion/optype.dart
@@ -466,6 +466,11 @@ class _OpTypeAstVisitor extends GeneralizingAstVisitor {
 
   @override
   void visitPropertyAccess(PropertyAccess node) {
+    if (node.realTarget is SimpleIdentifier && node.realTarget.isSynthetic) {
+      // If the access has no target (empty string)
+      // then don't suggest anything
+      return;
+    }
     if (identical(entity, node.operator) && offset > node.operator.offset) {
       // The cursor is between the two dots of a ".." token, so we need to
       // generate the completions we would generate after a "." token.