Fix null pointer (issue 24790)

pkg/analyzer/test/src/context/context_test.dart

Index: pkg/analyzer/test/src/context/context_test.dart
diff --git a/pkg/analyzer/test/src/context/context_test.dart b/pkg/analyzer/test/src/context/context_test.dart
index 39496e55c6dbd18f0a25e5e650e10d34ca6efc63..24d462289b6c9d982487e8423b1505bfdd687dbb 100644
--- a/pkg/analyzer/test/src/context/context_test.dart
+++ b/pkg/analyzer/test/src/context/context_test.dart
@@ -1441,6 +1441,11 @@ main() {}''');
     expect(context.isClientLibrary(source), isFalse);
   }
 
+  void test_isClientLibrary_unknown() {
+    Source source = newSource("/test.dart");
+    expect(context.isClientLibrary(source), isFalse);
+  }
+
   void test_isServerLibrary_dart() {
     Source source = addSource(
         "/test.dart",
@@ -1460,6 +1465,11 @@ main() {}''');
     expect(context.isServerLibrary(source), isFalse);
   }
 
+  void test_isServerLibrary_unknown() {
+    Source source = newSource("/test.dart");
+    expect(context.isServerLibrary(source), isFalse);
+  }
+
   void test_parseCompilationUnit_errors() {
     Source source = addSource("/lib.dart", "library {");
     CompilationUnit compilationUnit = context.parseCompilationUnit(source);