[kernel] Fix call to NameIndex(NULL)

runtime/vm/kernel_binary_flowgraph.cc

Index: runtime/vm/kernel_binary_flowgraph.cc
diff --git a/runtime/vm/kernel_binary_flowgraph.cc b/runtime/vm/kernel_binary_flowgraph.cc
index dec055dba6fbb19866275ad23170c33afddf2d56..8e1b0e1986cb78d29e37c6e79389f57c9aa117d4 100644
--- a/runtime/vm/kernel_binary_flowgraph.cc
+++ b/runtime/vm/kernel_binary_flowgraph.cc
@@ -1345,7 +1345,7 @@ const dart::String& StreamingFlowGraphBuilder::ReadNameAsMethodName() {
         ReadCanonicalNameReference();  // read library index.
     return H.DartMethodName(library_reference, name_index);
   } else {
-    return H.DartMethodName(NameIndex(NULL), name_index);
+    return H.DartMethodName(NameIndex(), name_index);
   }
 }
 
@@ -1356,7 +1356,7 @@ const dart::String& StreamingFlowGraphBuilder::ReadNameAsSetterName() {
         ReadCanonicalNameReference();  // read library index.
     return H.DartSetterName(library_reference, name_index);
   } else {
-    return H.DartSetterName(NameIndex(NULL), name_index);
+    return H.DartSetterName(NameIndex(), name_index);
   }
 }
 
@@ -1367,7 +1367,7 @@ const dart::String& StreamingFlowGraphBuilder::ReadNameAsGetterName() {
         ReadCanonicalNameReference();  // read library index.
     return H.DartGetterName(library_reference, name_index);
   } else {
-    return H.DartGetterName(NameIndex(NULL), name_index);
+    return H.DartGetterName(NameIndex(), name_index);
   }
 }