consumer_avformat: handle negative return value
consumer_avformat: handle negative return value

Fixes Coverity CID 709361: Argument cannot be negative (NEGATIVE_RETURNS)
Function "ftell(f)" returns a negative number.
Assigning: signed variable "size" = "ftell".
 937                                        size = ftell( f );
 938                                        fseek( f, 0, SEEK_SET );
 939                                        logbuffer = av_malloc( size + 1 );
At conditional (1): "!logbuffer" taking the false branch.
 940                                        if ( !logbuffer )
 941                                                mlt_log_fatal( MLT_CONSUMER_SERVICE( consumer ), "Could not allocate log buffer\n" );
 942                                        else
 943                                        {
"size" is passed to a parameter that cannot be negative.
 944                                                size = fread( logbuffer, 1, size, f );

siddharudh/mlt,j-b-m/mlt,j-b-m/mlt,gmarco/mlt-orig,anba8005/mlt,anba8005/mlt,zzhhui/mlt,anba8005/mlt,siddharudh/mlt,gmarco/mlt-orig,mltframework/mlt,siddharudh/mlt,gmarco/mlt-orig,zzhhui/mlt,zzhhui/mlt,wideioltd/mlt,mltframework/mlt,wideioltd/mlt,mltframework/mlt,anba8005/mlt,wideioltd/mlt,zzhhui/mlt,mltframework/mlt,zzhhui/mlt,siddharudh/mlt,gmarco/mlt-orig,j-b-m/mlt,anba8005/mlt,zzhhui/mlt,j-b-m/mlt,mltframework/mlt,wideioltd/mlt,gmarco/mlt-orig,gmarco/mlt-orig,mltframework/mlt,zzhhui/mlt,gmarco/mlt-orig,mltframework/mlt,siddharudh/mlt,mltframework/mlt,j-b-m/mlt,j-b-m/mlt,anba8005/mlt,xzhavilla/mlt,wideioltd/mlt,siddharudh/mlt,siddharudh/mlt,anba8005/mlt,mltframework/mlt,xzhavilla/mlt,j-b-m/mlt,xzhavilla/mlt,xzhavilla/mlt,gmarco/mlt-orig,zzhhui/mlt,wideioltd/mlt,xzhavilla/mlt,j-b-m/mlt,wideioltd/mlt,xzhavilla/mlt,j-b-m/mlt,xzhavilla/mlt,siddharudh/mlt,mltframework/mlt,xzhavilla/mlt,wideioltd/mlt,anba8005/mlt,xzhavilla/mlt,wideioltd/mlt,j-b-m/mlt,gmarco/mlt-orig,zzhhui/mlt,anba8005/mlt,siddharudh/mlt