Fix uses of ConditionBlock that require a condition expression (not a switch case statement)

Author: smowton

java/ql/lib/semmle/code/java/dataflow/Nullness.qll

@@ -460,7 +460,7 @@ private predicate interestingCond(SsaSourceVariable npecand, ConditionBlock cond
     varMaybeNullInBlock(_, npecand, cond, _) or
     varConditionallyNull(npecand.getAnSsaVariable(), cond, _)
   ) and
-  not cond.getCondition().getAChildExpr*() = npecand.getAnAccess()
+  not cond.getCondition().(Expr).getAChildExpr*() = npecand.getAnAccess()
 }
 
 /** A pair of correlated conditions for a given NPE candidate. */
@@ -588,7 +588,7 @@ private predicate trackingVar(
   exists(ConditionBlock cond |
     interestingCond(npecand, cond) and
     varMaybeNullInBlock(_, npecand, cond, _) and
-    cond.getCondition().getAChildExpr*() = trackvar.getAnAccess() and
+    cond.getCondition().(Expr).getAChildExpr*() = trackvar.getAnAccess() and
     trackssa.getSourceVariable() = trackvar and
     trackssa.getDefiningExpr().(VariableAssign).getSource() = init
   |