Branch condition evaluates to a garbage value in HGCalClusteringImpl

[jbsauvan]

Reported by scram b checker

L1Trigger/L1THGCal/src/backend/HGCalClusteringImpl.cc:87:26: warning: Branch condition evaluates to a garbage value [core.uninitialized.Branch]
    if (targetClu < 0 && isSeed[itc])
                         ^~~~~~~~~~~
L1Trigger/L1THGCal/src/backend/HGCalClusteringImpl.cc:301:9: warning: Branch condition evaluates to a garbage value [core.uninitialized.Branch]
    if (isSeed[itc])
        ^~~~~~~~~~~
L1Trigger/L1THGCal/src/backend/HGCalClusteringImpl.cc:392:9: warning: Branch condition evaluates to a garbage value [core.uninitialized.Branch]
    if (toRemove[i])
        ^~~~~~~~~~~