Fix 10599: regression- segmentation fault on template code (#3565)

Author: pfultz2

lib/checkbufferoverrun.cpp

@@ -999,6 +999,8 @@ void CheckBufferOverrun::objectIndex()
                 if (v.lifetimeKind != ValueFlow::Value::LifetimeKind::Address)
                     continue;
                 const Variable *var = v.tokvalue->variable();
+                if (!var)
+                    continue;
                 if (var->isReference())
                     continue;
                 if (var->isRValueReference())

test/testbufferoverrun.cpp

@@ -4750,6 +4750,15 @@ class TestBufferOverrun : public TestFixture {
               "    free(*str);\n"
               "}\n", "test.c");
         ASSERT_EQUALS("", errout.str());
+
+        check("template <typename T, unsigned N>\n"
+              "using vector = Eigen::Matrix<T, N, 1>;\n"
+              "template <typename V>\n"
+              "void scharr(image2d<vector<V, 2>>& out) {\n"
+              "    vector<V, 2>* out_row = &out(r, 0);\n"
+              "    out_row[c] = vector<V, 2>(1,2);\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
     }
 };