Add shortcut to avoid potential divide by zero in some case

uint32_t FontRenderer::getRemainingCacheCapacity() {

    uint32_t remainingCapacity = 0;

    float totalPixels = 0;

    //avoid divide by zero if the size is 0

    if (mCacheLines.size() == 0) {

        return 0;

    }

    for(uint32_t i = 0; i < mCacheLines.size(); i ++) {

         remainingCapacity += (mCacheLines[i]->mMaxWidth - mCacheLines[i]->mCurrentCol);

         totalPixels += mCacheLines[i]->mMaxWidth;