Don't reset timer in CBotStack::AllocateStack

The timer is already reset in CBotProgram::Run.
This prevents many cases where the game will hang or rendering is interrupted.
This fixes behavior of the script example in #874.
The script example in #971 doesn't hang the game anymore.

src/CBot/CBotStack.cpp

@@ -63,7 +63,6 @@ CBotStack* CBotStack::AllocateStack()
     memset(p, 0, size);
 
     p->m_block = BlockVisibilityType::BLOCK;
-    m_timer = m_initimer;                // sets the timer at the beginning
 
     CBotStack* pp = p;
     pp += MAXSTACK;