Fixed unmatched screen locking (locking only needed when writing to screen)

zsnes/src/linux/sdllink.c

@@ -995,9 +995,6 @@ void drawscreenwin(void)
     UpdateVFrame();
     if(curblank!=0) return;
     
-    Temp1=LockSurface();
-    if(Temp1==0) { return; }
-    
 #ifdef __OPENGL__
     if (UseOpenGL) {
 	
@@ -1035,6 +1032,9 @@ void drawscreenwin(void)
     } else {
 #endif
 
+        Temp1=LockSurface();
+        if(Temp1==0) { return; }
+    
 	ScreenPtr = vidbuffer;
 	ScreenPtr += 16*2+32*2+256*2;
 	SurfBufD = (DWORD) &SurfBuf[0];