Resolve bad cast to CJS_EventHandler

At line 2026 in pdfsdk/src/javascript/PublicMethods.cpp,
the writer wants to perform type cast like line 2027 but
he made a mistake to make type conversion on m_pValue.
Even at line 2027, it's redundant to make type conversion.
The returned type of pContext->GetEventHandler() is
CJS_EventHandler*.

BUG=529310
R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1325753007 .
diff --git a/fpdfsdk/src/javascript/PublicMethods.cpp b/fpdfsdk/src/javascript/PublicMethods.cpp
index c83ad05..1722d0f 100644
--- a/fpdfsdk/src/javascript/PublicMethods.cpp
+++ b/fpdfsdk/src/javascript/PublicMethods.cpp
@@ -2023,9 +2023,8 @@
   dValue = (double)floor(dValue * FXSYS_pow((double)10, (double)6) + 0.49) /
            FXSYS_pow((double)10, (double)6);
   CJS_Value jsValue(isolate, dValue);
-  if ((CJS_EventHandler*)pContext->GetEventHandler()->m_pValue)
-    ((CJS_EventHandler*)pContext->GetEventHandler())->Value() =
-        jsValue.ToCFXWideString();
+  if (pContext->GetEventHandler()->m_pValue)
+    pContext->GetEventHandler()->Value() = jsValue.ToCFXWideString();
 
   return TRUE;
 }