Add null checks before using element info

[mathroule]

Add null checks before using element info to fix issue #652.

[GaidamakUA]

Please, accept this pull request. I can't use stetho at all without these checks.

[growupzyg]

so,now which version should i use to avoid this issues? the newest version is 1.5.1 still has this problem

[ajdevy]

Here's the fix:

    implementation 'com.github.mathroule.stetho:stetho:bugfix~issue-652-SNAPSHOT'
    implementation("com.facebook.stetho:stetho-okhttp3:1.5.1") {
        exclude group: 'com.facebook.stetho'
    }

and add jitpack to your repositories:

buildscript {
    repositories {
        maven {
            url 'https://maven.fabric.io/public'
        }
    }
}

[gengjiawen]

cc @jasta