CID#1038307 Negative loop bound

fix of coverity#1038307 Negative loop bound
d9ac156b wasn't complete, it assigned possible
-1 int32 to unsigned value before comparison, so -1 not detected.

Change-Id: I6c2805acae8e776902d74c641e01c036193ce3d8

editeng/source/editeng/impedit2.cxx

@@ -1909,16 +1909,16 @@ void ImpEditEngine::InitWritingDirections( sal_Int32 nPara )
         ubidi_setPara( pBidi, reinterpret_cast<const UChar *>(aText.getStr()), aText.getLength(), nBidiLevel, NULL, &nError ); // UChar != sal_Unicode in MinGW
         nError = U_ZERO_ERROR;
 
-        size_t nCount = ubidi_countRuns( pBidi, &nError );
+        int32_t nCount = ubidi_countRuns( pBidi, &nError );
 
         /* ubidi_countRuns can return -1 in case of error */
-        if(nCount > 0)
+        if (nCount > 0)
         {
             int32_t nStart = 0;
             int32_t nEnd;
             UBiDiLevel nCurrDir;
 
-            for ( size_t nIdx = 0; nIdx < nCount; ++nIdx )
+            for (int32_t nIdx = 0; nIdx < nCount; ++nIdx)
             {
                 ubidi_getLogicalRun( pBidi, nStart, &nEnd, &nCurrDir );
                 rInfos.push_back( WritingDirectionInfo( nCurrDir, (sal_uInt16)nStart, (sal_uInt16)nEnd ) );