Core: Sidestep GCC false-positives

(cherry picked from commit acdb866)

Adds some more fixes for 4.5.

Co-authored-by: Rémi Verschelde <rverschelde@gmail.com>

Author: Repiteo

core/io/image.cpp

@@ -2338,6 +2338,10 @@ void Image::initialize_data(const char **p_xpm) {
 			} break;
 			case READING_PIXELS: {
 				int y = line - colormap_size - 1;
+#if defined(__GNUC__) && !defined(__clang__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic warning "-Wstringop-overflow=0"
+#endif
 				for (int x = 0; x < size_width; x++) {
 					char pixelstr[6] = { 0, 0, 0, 0, 0, 0 };
 					for (int i = 0; i < pixelchars; i++) {
@@ -2352,6 +2356,9 @@ void Image::initialize_data(const char **p_xpm) {
 					}
 					_put_pixelb(x, y, pixel_size, data_write, pixel);
 				}
+#if defined(__GNUC__) && !defined(__clang__)
+#pragma GCC diagnostic pop
+#endif
 
 				if (y == (size_height - 1)) {
 					status = DONE;

scene/resources/packed_scene.cpp

@@ -108,6 +108,7 @@ Node *SceneState::instantiate(GenEditState p_edit_state) const {
 	const NodeData *nd = &nodes[0];
 
 	Node **ret_nodes = (Node **)alloca(sizeof(Node *) * nc);
+	ret_nodes[0] = nullptr; // Sidesteps "maybe uninitialized" false-positives on GCC.
 
 	bool gen_node_path_cache = p_edit_state != GEN_EDIT_STATE_DISABLED && node_path_cache.is_empty();