CPP: Make InconsistentNullnessTest.cpp example plausible.

cpp/ql/src/Critical/InconsistentNullnessTesting.cpp

@@ -1,10 +1,10 @@
 void* f() {
-	block = malloc(BLOCK_SIZE);
+	block = (MyBlock *)malloc(sizeof(MyBlock));
 	if (block) { //correct: block is checked for nullness here
 		block->id = NORMAL_BLOCK_ID;
 	}
 	//...
 	/* make sure data-portion is null-terminated */
-	block[BLOCK_SIZE - 1] = '\0'; //wrong: block not checked for nullness here
+	block->data[BLOCK_SIZE - 1] = '\0'; //wrong: block not checked for nullness here
 	return block;
 }