Validate empty events

Invalid event

```json
{
"_id": {
"$oid": "5e552fc12ea83d67f04af745"
},
"groupHash": "9db3c43893911d5883caccc93b1b8d785d7c78c7df956ddd3ba3f6d4848a6bd4",
"payload": {
"timestamp": 1582641085.892,
"context": {},
"user": null,
"get": null,
"addons": {
"window": {}
},
"backtrace": [
{
"sourceCode": [
{},
{},
{
"content": ""
},
{},
{},
{},
{},
{},
{},
{},
{}
]
},
{
"sourceCode": [
{},
{
"content": ""
},
{},
{},
{
"content": ""
},
{},
{},
{},
{},
{},
{}
]
},
{
"sourceCode": [
{},
{},
{},
{},
{},
{},
{
"content": ""
},
{},
{},
{},
{
"content": ""
}
]
},
{
"sourceCode": [
{},
{
"content": ""
},
{},
{},
{
"content": ""
},
{},
{},
{},
{
"content": ""
},
{},
{}
]
},
{
"sourceCode": [
{},
{},
{},
{},
{},
{},
{
"content": ""
},
{},
{},
{},
{
"content": ""
}
]
},
{
"sourceCode": [
{},
{
"content": ""
},
{},
{},
{
"content": ""
},
{},
{},
{},
{
"content": ""
},
{},
{}
]
},
{
"sourceCode": [
{},
{},
{},
{},
{},
{},
{
"content": ""
},
{},
{},
{},
{
"content": ""
}
]
},
{
"sourceCode": [
{},
{
"content": ""
},
{},
{},
{
"content": ""
},
{},
{},
{},
{
"content": ""
},
{},
{}
]
},
{
"sourceCode": [
{},
{},
{},
{},
{},
{},
{
"content": ""
},
{},
{},
{},
{
"content": ""
}
]
},
{
"sourceCode": [
{},
{
"content": ""
},
{},
{},
{
"content": ""
},
{},
{},
{},
{
"content": ""
},
{},
{}
]
},
{
"sourceCode": [
{},
{},
{},
{},
{},
{},
{
"content": ""
},
{},
{},
{},
{
"content": ""
}
]
},
{
"sourceCode": null
}
]
}
}
```

Original event

```json
{
"_id": "5e5533462ea83d67f04b20df",
"groupHash": "9db3c43893911d5883caccc93b1b8d785d7c78c7df956ddd3ba3f6d4848a6bd4",
"payload": {
"timestamp": 1582641940.231,
"context": {},
"user": null,
"get": null,
"addons": {
"window": {
"innerWidth": 360,
"innerHeight": 704
}
},
"backtrace": [
{
"line": 105,
"column": 17,
"sourceCode": [
{
"line": 100,
"content": " \t\t\t\t\tscript.setAttribute(\"nonce\", __webpack_require__.nc);"
},
{
"line": 101,
"content": " \t\t\t\t}"
},
{
"line": 102,
"content": " \t\t\t\tscript.src = jsonpScriptSrc(chunkId);"
},
{
"line": 103,
"content": ""
},
{
"line": 104,
"content": " \t\t\t\t// create error before stack unwound to get useful stacktrace later"
},
{
"line": 105,
"content": " \t\t\t\tvar error = new Error();"
},
{
"line": 106,
"content": " \t\t\t\tonScri ptComplete = function (event) {"
},
{
"line": 107,
"content": " \t\t\t\t\t// avoid mem leaks in IE."
},
{
"line": 108,
"content": " \t\t\t\t\tscript.onerror = scri pt.onload = null;"
},
{
"line": 109,
"content": " \t\t\t\t\tclearTimeout(timeout);"
},
{
"line": 110,
"content": " \t\t\t\t\tvar chunk = installedChunks[chunkId];"
}
],
"function": "Function.o.e"
},
{
"sourceCode": [
{},
{
"content": ""
},
{},
{},
{
"content": ""
},
{},
{},
{},
{},
{},
{}
],
"function": "b .Air.define.init"
},
{
"line": 1350,
"column": 29,
"sourceCode": [
{
"line": 1345,
"content": " method.call(module.constructed, function () {"
},
{
"line": 1346,
"content": " check(method_name2, module_name, Date.now() - start_date2);"
},
{
"line": 1347,
"content": " });"
},
{
"line": 1348,
"content": " })(method_name, module.name, start_date);"
},
{
"line": 1349,
"content": " } else {"
},
{
"line": 1350,
"content": " method.call(module.constructed);"
},
{
"line": 1351,
"content": " check(meth od_name, module.name, Date.now() - start_date);"
},
{
"line": 1352,
"content": " }"
},
{
"line": 1353,
"content": " } catch (er ror) {"
},
{
"line": 1354,
"content": " console.error('[ Air ] processModules: error while %s \"%s\": %s', method_name, module.name, error.message );"
},
{
"line": 1355,
"content": ""
}
]
},
{
"line": 1321,
"column": 16,
"sourceCode": [
{
"line": 1316,
"content": " // self.utility.log('%s \"%s\" ', capitilize(method_name2), module_name);"
},
{
"line": 1317,
"content": " // }"
},
{
"line": 1318,
"content": ""
},
{
"line": 1319,
"content": " if (counter === w_modules_length) {"
},
{
"line": 1320,
"content": " if (current_weight !== finish_weight) {"
},
{
"line": 1321,
"content": " runWithWeight(current_weight + shift);"
},
{
"line": 1322,
"content": " } else {"
},
{
"line": 1323,
"content": " callba ck && callback(global_counter);"
},
{
"line": 1324,
"content": " }"
},
{
"line": 1325,
"content": " }"
},
{
"line": 1326,
"content": " };"
}
]
},
{
"line": 1351,
"column": 22,
"sourceCode": [
{
"line": 1346,
"content": " check(method_name2, module_name, Date.now() - start_date2);"
},
{
"line": 1347,
"content": " });"
},
{
"line": 1348,
"content": " })(method_name, module.name, star t_date);"
},
{
"line": 1349,
"content": " } else {"
},
{
"line": 1350,
"content": " method.call(module.constructed);"
},
{
"line": 1351,
"content": " check(method_name, module.name, Date.now() - start_date);"
},
{
"line": 1352,
"content": " }"
},
{
"line": 1353,
"content": " } catch (error) {"
},
{
"line": 1354,
"content": " console.error('[ Air ] processModules: error w hile %s \"%s\": %s', method_name, module.name, error.message);"
},
{
"line": 1355,
"content": ""
},
{
"line": 1356,
"content": " if (self.is_deb ug === true) {"
}
]
},
{
"line": 1321,
"column": 16,
"sourceCode": [
{
"line": 1316,
"content": " // self.utility.log('%s \"%s\"', capitilize(method_na me2), module_name);"
},
{
"line": 1317,
"content": " // }"
},
{
"line": 1318,
"content": ""
},
{
"line": 1319,
"content": " if (counter === w_modules_length) {"
},
{
"line": 1320,
"content": " if (current_weight !== finish_weight) {"
},
{
"line": 1321,
"content": " runWithW eight(current_weight + shift);"
},
{
"line": 1322,
"content": " } else {"
},
{
"line": 1323,
"content": " callback && callback(global_c ounter);"
},
{
"line": 1324,
"content": " }"
},
{
"line": 1325,
"content": " }"
},
{
"line": 1326,
"content": " };"
}
]
},
{
"li ne": 1351,
"column": 22,
"sourceCode": [
{
"line": 1346,
"content": " check(method_name2, module_name, Date.now() - start_date2);"
},
{
" line": 1347,
"content": " });"
},
{
"line": 1348,
"content": " })(method_name, module.name, start_date);"
},
{
"line": 1349,
"content": " } else {"
},
{
"line": 1350,
"content": " method.call(module.constructed);"
},
{
"line": 1351,
"content ": " check(method_name, module.name, Date.now() - start_date);"
},
{
"line": 1352,
"content": " }"
},
{
"line": 1353,
"cont ent": " } catch (error) {"
},
{
"line": 1354,
"content": " console.error('[ Air ] processModules: error while %s \"%s\": %s', me thod_name, module.name, error.message);"
},
{
"line": 1355,
"content": ""
},
{
"line": 1356,
"content": " if (self.is_debug === true) {"
}
]
},
{
"line": 1321,
"column": 16,
"sourceCode": [
{
"line": 1316,
"content": " // self.utility.log('%s \"%s\"', capitilize(method_name2), module_name);"
},
{
"line": 1317,
"content": " // }"
},
{
"line": 1318,
"content": ""
},
{
"line": 1319,
"content": " if (counter === w_modules_length) {"
},
{
"line": 1320,
"content": " if (current_weight !== finish_weight) {"
},
{
"line": 1321,
"content": " runWithWeight(current_weight + shift);"
},
{
"line": 1322,
"content": " } else {"
},
{
"line": 1323,
"content": " callback && callback(global_counter);"
},
{
"line": 1324,
"content": " }"
},
{
"line": 1325,
"content": " }"
},
{
"line": 1326,
"content": " };"
}
]
},
{
"line": 1351,
"column": 22,
"sourceCode": [
{
"line": 1346,
"content": " check(method_name2, module_name, Date.now() - start_date2);"
},
{
"line": 1347,
"content": " });"
},
{
"line": 1348,
"content": " })(method_name, module.name, start_date);"
},
{
"line": 1349,
"content": " } else {"
},
{
"line": 1350,
"content": " method.call(module.constructed);"
},
{
"line": 1351,
"content": " check(method_name, module.name, Date.now() - start_date);"
},
{
"line": 1352,
"content": " }"
},
{
"line": 1353,
"content": " } catch (error) {"
},
{
"line": 1354,
"content": " console.error('[ Air ] processModules: error while %s \"%s\": %s', method_name, module.name, error.message);"
},
{
"line": 1355,
"content": ""
},
{
"line": 1356,
"content": " if (self.is_debug === true) {"
}
]
},
{
"line": 1321,
"colum n": 16,
"sourceCode": [
{
"line": 1316,
"content": " // self.utility.log('%s \"%s\"', capitilize(method_name2), module_name);"
},
{
"line": 1317,
"cont ent": " // }"
},
{
"line": 1318,
"content": ""
},
{
"line": 1319,
"content": " if (counter === w_modules_length) {"
},
{
"line": 1320,
"con tent": " if (current_weight !== finish_weight) {"
},
{
"line": 1321,
"content": " runWithWeight(current_weight + shift);"
},
{
"line": 1322,
"content": " } else {"
},
{
"line": 1323,
"content": " callback && callback(global_counter);"
},
{
"line": 1324,
"content": " }"
},
{
"line": 1325,
"content": " }"
},
{
"line": 1326,
"content": " };"
}
]
}
]
}
}

```