Fix for #1715

Old & annoying; error() menu doesnt work while rendering, and is still
called for many occsasions. Error also caused Blender window to screw up.

Now error() just prints during render.

source/blender/src/toolbox.c

@@ -109,6 +109,7 @@
 
 #include "mydevice.h"
 #include "blendef.h"
+#include "render.h"
 
 static int tbx1, tbx2, tby1, tby2, tbfontyofs, tbmain=0;
 static int tbmemx=TBOXX/2, tbmemy=(TBOXEL-0.5)*TBOXH, tboldwin, addmode= 0;
@@ -1087,7 +1088,7 @@ void error(char *fmt, ...)
 	sprintf(nfmt, "ERROR: %s", fmt);
 
 	va_start(ap, fmt);
-	if (G.background || !G.curscreen) {
+	if (G.background || !G.curscreen || (R.flag & R_RENDERING)) {
 		vprintf(nfmt, ap);
 		printf("\n");
 	} else {