Check for EOF to fix a segfault while parsing fuzzed MPC files.

tests/data/segfault2.mpc

@@ -0,0 +1 @@
+MPCKSH

tests/test_mpc.cpp

@@ -20,6 +20,7 @@ class TestMPC : public CppUnit::TestFixture
   CPPUNIT_TEST(testFuzzedFile1);
   CPPUNIT_TEST(testFuzzedFile2);
   CPPUNIT_TEST(testFuzzedFile3);
+  CPPUNIT_TEST(testFuzzedFile4);
   CPPUNIT_TEST_SUITE_END();
 
 public:
@@ -82,6 +83,12 @@ public:
     CPPUNIT_ASSERT(f.isValid());
   }
 
+  void testFuzzedFile4()
+  {
+    MPC::File f(TEST_FILE_PATH_C("segfault2.mpc"));
+    CPPUNIT_ASSERT(f.isValid());
+  }
+
 };
 
 CPPUNIT_TEST_SUITE_REGISTRATION(TestMPC);