imm32: Exit on invalid window in ImmAssociateContext.

dlls/imm32/imm.c

@@ -583,12 +583,13 @@ BOOL WINAPI ImmSetActiveContext(HWND hwnd, HIMC himc, BOOL activate)
  */
 HIMC WINAPI ImmAssociateContext(HWND hWnd, HIMC hIMC)
 {
-    HIMC old = NULL;
     InputContextData *data = get_imc_data(hIMC);
+    HIMC defaultContext;
+    HIMC old;
 
     TRACE("(%p, %p):\n", hWnd, hIMC);
 
-    if(hIMC && !data)
+    if (!IsWindow(hWnd) || (hIMC && !data))
         return NULL;
 
     /*
@@ -600,11 +601,8 @@ HIMC WINAPI ImmAssociateContext(HWND hWnd, HIMC hIMC)
     if (hIMC && IMM_IsCrossThreadAccess(hWnd, hIMC))
         return NULL;
 
-    if (hWnd)
-    {
-        HIMC defaultContext = get_default_context( hWnd );
-        old = RemovePropW(hWnd,szwWineIMCProperty);
-
+    defaultContext = get_default_context( hWnd );
+    old = RemovePropW(hWnd, szwWineIMCProperty);
     if (old == NULL)
         old = defaultContext;
     else if (old == (HIMC)-1)
@@ -613,9 +611,9 @@ HIMC WINAPI ImmAssociateContext(HWND hWnd, HIMC hIMC)
     if (hIMC != defaultContext)
     {
         if (hIMC == NULL) /* Meaning disable imm for that window*/
-                SetPropW(hWnd,szwWineIMCProperty,(HANDLE)-1);
+            SetPropW(hWnd, szwWineIMCProperty, (HANDLE)-1);
         else
-                SetPropW(hWnd,szwWineIMCProperty,hIMC);
+            SetPropW(hWnd, szwWineIMCProperty, hIMC);
     }
 
     if (old)
@@ -624,7 +622,6 @@ HIMC WINAPI ImmAssociateContext(HWND hWnd, HIMC hIMC)
         if (old_data->IMC.hWnd == hWnd)
             old_data->IMC.hWnd = NULL;
     }
-    }
 
     if (!hIMC)
         return old;