Fix possible out of bounds issue

diff --git a/MagickCore/fx.c b/MagickCore/fx.c
index 583a478dfe2f607d503578e83890015764162070..52b206da836e2bc886555cb74edc99b97e25ad04 100644 (file)
--- a/MagickCore/fx.c
+++ b/MagickCore/fx.c
@@ -2372,7 +2372,8 @@ static double FxEvaluateSubexpression(FxInfo *fx_info,
         (void) ThrowMagickException(exception,GetMagickModule(),OptionError,
           "ParenthesisNestedTooDeeply","`%s'",expression);
       (void) CopyMagickString(subexpression,expression+1,MagickPathExtent);
-      subexpression[strlen(subexpression)-1]='\0';
+      if (strlen(subexpression) != 0)
+        subexpression[strlen(subexpression)-1]='\0';
       gamma=FxEvaluateSubexpression(fx_info,channel,x,y,subexpression,depth,
         beta,exception);
       (*depth)--;