Fail gracefully in Script::GetLine under precompilation like Script::GetSnippet.

runtime/vm/object.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 8789 matching lines @@
          tkit.CurrentTokenKind() != Token::kEOS) {
     end_pos = tkit.CurrentPosition();
     tkit.Advance();
   }
   *last_token_index = end_pos;
 }
 
 
 RawString* Script::GetLine(intptr_t line_number, Heap::Space space) const {
   const String& src = String::Handle(Source());
+  if (src.IsNull()) {
+    ASSERT(Dart::IsRunningPrecompiledCode());
+    return Symbols::OptimizedOut().raw();
+  }
   intptr_t relative_line_number = line_number - line_offset();
   intptr_t current_line = 1;
   intptr_t line_start_idx = -1;
   intptr_t last_char_idx = -1;
   for (intptr_t ix = 0;
        (ix < src.Length()) && (current_line <= relative_line_number);
        ix++) {
     if ((current_line == relative_line_number) && (line_start_idx < 0)) {
       line_start_idx = ix;
     }
@@ skipping 13097 matching lines @@
   return UserTag::null();
 }
 
 
 const char* UserTag::ToCString() const {
   const String& tag_label = String::Handle(label());
   return tag_label.ToCString();
 }
 
 }  // namespace dart