frei0r/factory.c: fix possible buffer overflow and null dereference
frei0r/factory.c: fix possible buffer overflow and null dereference

Fixes Coverity CID 709415: Copy into fixed size buffer (STRING_OVERFLOW)
You might overrun the 1024 byte fixed-size string "pluginname" by copying "firstname" without checking the length.
390                        strcat(pluginname,firstname);

and

CID 709397: Dereference before null check (REVERSE_INULL)
Dereferencing pointer "firstname". (The dereference is assumed on the basis of the 'nonnull' parameter attribute.)
390                        strcat(pluginname,firstname);

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