Guard StatusBarManager methods against pre-build AttributeError

[Copilot]

StatusBarManager.update_warnings() and try_update() accessed self.bar unconditionally, but self.bar is only assigned in build(). Any call before build() would raise AttributeError.

Changes

• __init__: initialize self.bar: Optional[Container] = None so the attribute always exists at construction time
• update_warnings(): wrap the bar.bgcolor update in if self.bar is not None: — warning item visibility is still updated regardless
• try_update(): early-return if self.bar is None instead of letting the bare except swallow the error

# Before: AttributeError silently swallowed
def try_update(self):
    try:
        self.bar.update()  # AttributeError if build() not yet called
    except Exception:
        pass

# After: explicit guard, no silent failure
def try_update(self):
    if self.bar is None:
        return
    try:
        self.bar.update()
    except Exception:
        pass

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