Fix incorrect MemberRefExpr::getQualifier() usage

`MemberRefExpr::getQualifier()` actually obtains the qualifier of the
synthetic anonymous class creation representing the method reference
expression, and therefore does not have the desired (or any) result.

Author: Marcono1234

codeql-custom-queries-java/queries/lib/Expressions.qll

@@ -153,7 +153,7 @@ class CallableReferencingExpr extends Expr {
     Expr getQualifier() {
         result = [
             this.(MethodAccess).getQualifier(),
-            this.(MemberRefExpr).getQualifier(),
+            this.(MemberRefExpr).getReceiverExpr(),
             this.(ClassInstanceExpr).getQualifier(),
         ]
     }

codeql-custom-queries-java/queries/recommendations/catch-clause-logging-and-throwing-exception.ql

@@ -579,7 +579,7 @@ private predicate referencesVariable(Expr expr, Variable var) {
         (
             m = expr.(MethodAccess).getMethod() and referencesVariable(expr.(MethodAccess).getQualifier(), var)
             or m = expr.(FieldAccess).getField() and referencesVariable(expr.(FieldAccess).getQualifier(), var)
-            or m = expr.(MemberRefExpr).getReferencedCallable() and referencesVariable(expr.(MemberRefExpr).getQualifier(), var)
+            or m = expr.(MemberRefExpr).getReferencedCallable() and referencesVariable(expr.(MemberRefExpr).getReceiverExpr(), var)
         )
         // Ignore if instance is used for static member access (which itself is bad code style)
         and not m.isStatic()