[Issue] 50.11 Mek Lab NullPointerException

[splyncryth]

Brief Description *

With a dropship loaded into the MHQ Mek Lab, removing a weapons bay from the nose or aft causes a NullPointerException. Subsequently, after closing out the error message if I go into Equipment and try to add a weapon I also get a NullPointerException.

This happens in 50.10 and 50.11

3. Steps to Reproduce

No response

Attach Files

mekhq.log

Bug.cpnx.gz

Severity *

Critical (Game-breaking/Crash): The game crashes or a core feature (like saving, loading, or network connection) is completely unusable.

MekHQ Suite Version *

50.10 and 50.11

Operating System *

XUbuntu

Java Version *

17

Final Verification

• I confirm this is a single, unique issue that hasn't been reported before
• I have filled and provided all necessary information above
• I have included any and all logs, custom units, and CPNX (save) files
• I have asked on MegaMek Discord about this issue
• I have confirmed this issue is being opened on the correct repository: MegaMek, MegaMekLab, or MekHQ

[HammerGS]

10:32:37,394 ERROR [mekhq.MekHQ] {AWT-EventQueue-0}
mekhq.MekHQ.lambda$main$1(MekHQ.java:376) - Uncaught java.lang.NullPointerException detected. Please open up an issue containing all logs, the game save file, and customs at https://github.com/MegaMek/megamek/issues . If Sentry is enabled, the error has also been logged.
java.lang.NullPointerException: Cannot invoke "mekhq.campaign.unit.Unit.getEntity()" because "this.unit" is null
	at mekhq.campaign.parts.missing.MissingFireControlSystem.getBaseTime(MissingFireControlSystem.java:73)
	at mekhq.campaign.parts.Refit.calculate(Refit.java:601)
	at mekhq.campaign.parts.Refit.<init>(Refit.java:208)
	at mekhq.gui.MekLabTab.refreshRefitSummary(MekLabTab.java:336)
	at mekhq.gui.MekLabTab$DropshipPanel.refreshStatus(MekLabTab.java:785)
	at megameklab.ui.util.AbstractEquipmentDatabaseView.fireTableRefresh(AbstractEquipmentDatabaseView.java:487)
	at megameklab.ui.util.AbstractEquipmentDatabaseView.addSelectedEquipment(AbstractEquipmentDatabaseView.java:470)
	at megameklab.ui.util.AbstractEquipmentDatabaseView$AddAction.actionPerformed(AbstractEquipmentDatabaseView.java:652)

[HammerGS]

Bug Analysis: Issue #2103 - MekLab NullPointerException

Root Cause

The bug is in MegaMekLab's BayWeaponCriticalTree.java which MekHQ uses. The refresh field is called without null checks in multiple locations:

BayWeaponCriticalTree.java lines 350-354, 417-421, 454-458, etc:
if (shouldRefresh) {
refresh.refreshEquipment(); // NPE if refresh is null
refresh.refreshBuild();
refresh.refreshPreview();
refresh.refreshStatus();
refresh.refreshSummary();
}

Why It Happens

1. When LABuildTab is constructed, it passes null as the refresh listener to LACriticalView (LABuildTab.java line 76)
2. LACriticalView creates BayWeaponCriticalTree instances with this null refresh (LACriticalView.java line 117-119)
3. The refresh listener is set later via addRefreshedListener(), but if there's a timing issue or the user interacts before setup completes, NPE occurs

Affected Files

• megameklab/megameklab/src/megameklab/ui/util/BayWeaponCriticalTree.java - Missing null checks for refresh
• This is MegaMekLab code, not MekHQ code - the fix should be in the megameklab project

Recommended Fix

Add null checks before calling refresh methods, e.g.:
if (shouldRefresh && refresh != null) {
refresh.refreshEquipment();
// ...
}