Ensure mUri is not null in Window save

[bluemarvin]

Speculative fix for https://crash-stats.mozilla.org/report/index/6b13ce7f-7f54-48f3-acf4-ebb540200428

[keianhzo]

Seeing at the crash, looks like it must be that. Can we make it in a single line? like:

.filter(sessionState -> SAVE_BLACKLIST.stream().noneMatch(uri ->
                            sessionState.mUri == null || sessionState.mUri.startsWith(uri)))

[bluemarvin]

Seeing at the crash, looks like it must be that. Can we make it in a single line? like:

.filter(sessionState -> SAVE_BLACKLIST.stream().noneMatch(uri ->
                            sessionState.mUri == null || sessionState.mUri.startsWith(uri)))

Shouldn't it be sessionState.mUri != null && sessionState.mUri.startsWith(uri)))