Fix missing error when accessing unintialized variables.

test/libsolidity/syntaxTests/controlFlow/uninitializedAccess/bug10821-modifier.sol

@@ -0,0 +1,16 @@
+contract Test {
+
+  struct Sample { bool flag; }
+  Sample public s;
+
+  modifier checkAddr(address _a){
+      require(_a!=address(0));
+      _;
+  }
+  function testFunc(address _a) external checkAddr(_a) {
+        Sample storage t;
+        t.flag=true;
+    }
+}
+// ----
+// TypeError 3464: (237-238): This variable is of storage pointer type and can be accessed without prior assignment, which would lead to undefined behaviour.