In Function X11_DispatchEvent(_THIS), case SelectionNotify :
static void
X11_DispatchEvent(_THIS)
{
 // Some Code
  case SelectionNotify: {
  //Some Code
  SDL_bool expect_lf = SDL_FALSE;
                    char *start = NULL; // Initialised with NULL
                    char *scan = (char*)p.data;
                    char *fn;
                    char *uri;
                    int length = 0;
                    while (p.count--) {
                        if (!expect_lf) {
                            if (*scan==0x0D) {
                                expect_lf = SDL_TRUE;
                            } else if(start == NULL) {
                                start = scan;
                                length = 0;
                            }
                            length++;
                        } else {
                            if (*scan==0x0A && length>0) {
                                uri = malloc(length--);

                                memcpy(uri, start, length); // Problem is Here, start is still NULL if control comes to else statement without initialising the start pointer, which is wrong

                                uri[length] = 0;
                                fn = X11_URIToLocal(uri);
                                if (fn) SDL_SendDropFile(fn);
                                free(uri);
                            }
                            expect_lf = SDL_FALSE;
                            start = NULL;
                        }
                        scan++;
                    }
                }
As shown above how start pointer remains NULL, Patch for this issue would be:
                            if (*scan==0x0D) {
                                expect_lf = SDL_TRUE;
                            } 
                            if(start == NULL) {
                                start = scan;
                                length = 0;
                            }
Just replace else if statement with if.

Thanks,
Nitz