Fixed #2141 (false positive: possible null pointer dereference)

lib/checkother.cpp

@@ -2543,6 +2543,8 @@ void CheckOther::nullPointerByCheckAndDeRef()
         {
             bool null = true;
             const unsigned int varid(tok->tokAt(3)->varId());
+            if (varid == 0)
+                continue;
             unsigned int indentlevel = 1;
             for (const Token *tok2 = tok->tokAt(6); tok2; tok2 = tok2->next())
             {

test/testother.cpp

@@ -1197,6 +1197,13 @@ private:
                          "}\n");
         ASSERT_EQUALS("", errout.str());
 
+        checkNullPointer("void foo() {\n"
+                         "    if (!p) {\n"
+                         "        switch (x) { }\n"
+                         "    }\n"
+                         "}\n");
+        ASSERT_EQUALS("", errout.str());
+
     }
 
     void checkUninitVar(const char code[])