Fix the "bahro climbing a ladder" crash

This fix will cause the armature brain to skip over animations that it doesn't have data for, rather than crashing. If you're in debug mode, you'll get a nice assert as well.

Sources/Plasma/PubUtilLib/plAvatar/plAnimStage.cpp

@@ -425,6 +425,14 @@ bool plAnimStage::IMoveBackward(double time, float delta, float &overrun, plArma
     bool infiniteLoop = fLoops == -1;
     bool loopsRemain = fCurLoop > 0 || infiniteLoop;
 
+    // If we don't have this animation, just pretend to have worked.
+    // Otherwise, we crash the client.
+    if (!fAnimInstance)
+    {
+        hsAssert(false, "AnimInstance nil");
+        return true;
+    }
+
     // This must be here before we set the local time.
     if (fAnimInstance->GetTimeConvert())
         fAnimInstance->GetTimeConvert()->Backwards();
@@ -477,6 +485,14 @@ bool plAnimStage::IMoveForward(double time, float delta, float &overrun, plArmat
     // first get the target time in local time, ignoring overruns
     float target = fLocalTime + delta;
 
+    // If we don't have this animation, just pretend to have worked.
+    // Otherwise, we crash the client.
+    if (!fAnimInstance)
+    {
+        hsAssert(false, "AnimInstance nil");
+        return true;
+    }
+
     if (fAnimInstance->GetTimeConvert())
         fAnimInstance->GetTimeConvert()->Forewards();