fix #215 gdImageFillToBorder stack-overflow when invalid color is used

src/gd.c

@@ -1928,11 +1928,17 @@ BGD_DECLARE(void) gdImageFillToBorder (gdImagePtr im, int x, int y, int border,
 	int i;
 	int restoreAlphaBleding;
 
-	if (border < 0) {
+	if (border < 0 || color < 0) {
 		/* Refuse to fill to a non-solid border */
 		return;
 	}
 
+	if (!im->trueColor) {
+		if ((color > (im->colorsTotal - 1)) || (border > (im->colorsTotal - 1))) {
+			return;
+		}
+    }
+
 	leftLimit = (-1);
 
 	restoreAlphaBleding = im->alphaBlendingFlag;

tests/gdimagefilltoborder/.gitignore

@@ -1 +1,2 @@
 /bug00037
+/github_bug_215

tests/gdimagefilltoborder/CMakeLists.txt

@@ -1,5 +1,6 @@
 SET(TESTS_FILES
 	bug00037
+	github_bug_215
 )
 
 ADD_GD_TESTS()

tests/gdimagefilltoborder/Makemodule.am

@@ -1,6 +1,7 @@
 if HAVE_LIBPNG
 libgd_test_programs += \
-	gdimagefilltoborder/bug00037
+	gdimagefilltoborder/bug00037 \
+	gdimagefilltoborder/github_bug_215
 endif
 
 EXTRA_DIST += \