Add missing checks for null imported/exportedLibraries.

pkg/analyzer/lib/src/generated/element_resolver.dart

Index: pkg/analyzer/lib/src/generated/element_resolver.dart
diff --git a/pkg/analyzer/lib/src/generated/element_resolver.dart b/pkg/analyzer/lib/src/generated/element_resolver.dart
index b1c5283b5a4c3080907601f9387279002941f8a0..4dd9726bc298f6b63391f79bb44ea0682167d843 100644
--- a/pkg/analyzer/lib/src/generated/element_resolver.dart
+++ b/pkg/analyzer/lib/src/generated/element_resolver.dart
@@ -626,7 +626,8 @@ class ElementResolver extends SimpleAstVisitor<Object> {
             [(target as SimpleIdentifier).name]);
       }
       LibraryElement importedLibrary = _getImportedLibrary(target);
-      FunctionElement loadLibraryFunction = importedLibrary.loadLibraryFunction;
+      FunctionElement loadLibraryFunction =
+          importedLibrary?.loadLibraryFunction;
       methodName.staticElement = loadLibraryFunction;
       node.staticInvokeType = loadLibraryFunction.type;
       return null;
@@ -894,7 +895,7 @@ class ElementResolver extends SimpleAstVisitor<Object> {
     if (identifier.name == FunctionElement.LOAD_LIBRARY_NAME &&
         _isDeferredPrefix(prefix)) {
       LibraryElement importedLibrary = _getImportedLibrary(prefix);
-      identifier.staticElement = importedLibrary.loadLibraryFunction;
+      identifier.staticElement = importedLibrary?.loadLibraryFunction;
       return null;
     }
     //