rem: var script = sourceFile.getScriptByLineNumer(line); if (!script) FBTrace.sysout("Need to build line table or line is not executable\n"); 
add: if (sourceFile) var script = sourceFile.getScriptByLineNumber(line); else FBTrace.sysout("lib.findScript, no sourceFile in context for url=", url); 
context: this.findScript = function(context, url, line){    var sourceFile = context.sourceFileMap[url];    var script = sourceFile.getScriptByLineNumer(line);    if (!script)        FBTrace.sysout("Need to build line table or line is not executable\n");    return script;};
meta: 7450	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/7450/e94319b3c9f6fd8d1ba545aed3ffde4b9acb13a7/lib.js/buggy/extension/content/firebug/lib.js