ValueFlow: Fix crash

lib/valueflow.cpp

@@ -4945,6 +4945,8 @@ static void valueFlowForwardAssign(Token* const tok,
 
     // Skip RHS
     const Token * nextExpression = tok->astParent() ? nextAfterAstRightmostLeaf(tok->astParent()) : tok->next();
+    if (!nextExpression)
+        return;
 
     for (ValueFlow::Value& value : values) {
         if (value.isSymbolicValue())

test/testvalueflow.cpp

@@ -6259,6 +6259,13 @@ private:
                "  }\n"
                "};\n";
         valueOfTok(code, "f.c");
+
+        code = "int f(int value) { return 0; }\n"
+               "std::shared_ptr<Manager> g() {\n"
+               "    static const std::shared_ptr<Manager> x{ new M{} };\n"
+               "    return x;\n"
+               "}\n";
+        valueOfTok(code, "x");
     }
 
     void valueFlowHang() {