rtspconnection: GError set over the top of a previous GError or uninitialized memory.

Submitted by Nils Öhnell

Link to original bug (#795596)

Description

file: gstrtspconnection.c
functions: read_bytes(), write_bytes(), fill_bytes()

The functions do not have handling for the situation that sub-functions return both a positive number of bytes and an error at the same time.

The problem is discovered in the next lap of the while-loop when the error has not been cleared from the previous lap, and this error print is issued:
"GError set over the top of a previous GError or uninitialized memory."