fix for a handful of memory leaks relating to parsing and allocating arbitrary sized vectors from python args.

Vector.dot() was always leaking memory, and would crash if args sizes didnt match.

These errors were introduced with n-dimensional vector support.

also fixed an error with bmesh py api allocation.

source/blender/python/mathutils/mathutils.c

@@ -133,6 +133,7 @@ int mathutils_array_parse(float *array, int array_min, int array_max, PyObject *
 	}
 }
 
+/* on error, -1 is returned and no allocation is made */
 int mathutils_array_parse_alloc(float **array, int array_min, PyObject *value, const char *error_prefix)
 {
 	int size;
@@ -164,6 +165,7 @@ int mathutils_array_parse_alloc(float **array, int array_min, PyObject *value, c
 	{
 		PyObject *value_fast = NULL;
 		// *array = NULL;
+		int ret;
 
 		/* non list/tuple cases */
 		if (!(value_fast = PySequence_Fast(value, error_prefix))) {
@@ -182,7 +184,13 @@ int mathutils_array_parse_alloc(float **array, int array_min, PyObject *value, c
 
 		*array = PyMem_Malloc(size * sizeof(float));
 
-		return mathutils_array_parse_fast(*array, size, value_fast, error_prefix);
+		ret = mathutils_array_parse_fast(*array, size, value_fast, error_prefix);
+
+		if (ret == -1) {
+			PyMem_Free(*array);
+		}
+
+		return ret;
 	}
 }