Fixes logically dead code (Coverity)

Fixes reported logically dead codes by Coverity

* image.cpp: Doesn't really need any modification. But to remove the bug
report then we have to move the MAX call away from the for loop
statement.

* rasterizer_gles3.cpp: Removes unnecessary elif condition since it is
checked earlier in the function

* collada.cpp: If stamement never reached due to macro ERR_CONTINUE does
the same.

* navigation_mesh.cpp: Variables should always be null - however, also
checked for the very same condition in their function call. Leaving this
for review (whether the function call is necessary or not)

* path_editor_plugin.cpp: If cancel is true, then it should restore the
edited value to the original provided.
http://docs.godotengine.org/en/3.0/classes/class_editorspatialgizmo.html#class-editorspatialgizmo-commit-handle

* spatial_editor_gizmos.cpp: the very condition of i >= 3 is
predetermined in the if case right before it. Thus case 1 is always '1'
and case 2 is always '-1'

* grid_map_editor.cpp: Same as above in spatial_editor_gizmos.cpp

* voxel_light_baker.cpp: Same as above in spatial_editor_gizmos.cpp

* visual_server.cpp: Same as above in spatial_editor_gizmos.cpp

* visual_script_expression.cpp: char '-' is already true in the switch
case mechanism. Thus it can never reach to default case.

* particles.cpp: Case 'PARAM_MAX' is unreachable due to index checking
right before the switch execution.

* shader_language.cpp: Invalid index is handled in switch default case.
`type < TYPE_FLOAT && type > TYPE_VEC4` -> `(type < TYPE_FLOAT || type > TYPE_VEC4`)
Fixes the "always false problem" in TODO comment.

1 files changed, 2 insertions, 2 deletions

diff --git a/modules/gridmap/grid_map_editor_plugin.cpp b/modules/gridmap/grid_map_editor_plugin.cpp
index f523eef895..4b96824dca 100644
--- a/modules/gridmap/grid_map_editor_plugin.cpp
+++ b/modules/gridmap/grid_map_editor_plugin.cpp
@@ -1154,9 +1154,9 @@ GridMapEditor::GridMapEditor(EditorNode *p_editor) {
 				for (int k = 0; k < 3; k++) {
 
 					if (i < 3)
-						face_points[j][(i + k) % 3] = v[k] * (i >= 3 ? -1 : 1);
+						face_points[j][(i + k) % 3] = v[k];
 					else
-						face_points[3 - j][(i + k) % 3] = v[k] * (i >= 3 ? -1 : 1);
+						face_points[3 - j][(i + k) % 3] = -v[k];
 				}
 			}