[dataflow] fix assert in Environment::getResultObjectLocation

When calling `Environment::getResultObjectLocation` with a
CXXOperatorCallExpr that is a prvalue, we just hit an assert because no
record was ever created.

Author: paulsemel

clang/lib/Analysis/FlowSensitive/Transfer.cpp

@@ -536,6 +536,11 @@ class TransferVisitor : public ConstStmtVisitor<TransferVisitor> {
 
       copyRecord(*LocSrc, *LocDst, Env);
       Env.setStorageLocation(*S, *LocDst);
+    } else {
+      // CXXOperatorCallExpr can be prvalues, in which case we must create a
+      // record for them in order for `Environment::getResultObjectLocation()`
+      // to be able to return a value.
+      VisitCallExpr(S);
     }
   }